@article {25583, title = {Ultrafast fs coherent excitonic dynamics in CdSe quantum dots assemblies addressed and probed by 2D electronic spectroscopy}, journal = {Journal of Chemical Physics}, volume = {154}, number = {1}, year = {2021}, note = {Collini, Elisabetta Gattuso, Hugo Levine, R. D. Remacle, F.}, type = {Journal Article}, doi = {10.1063/5.0031420}, author = {Collini, E. and Gattuso, H. and Levine, R. D. and Remacle, F.} } @article {25582, title = {Ultrafast geometrical reorganization of a methane cation upon sudden ionization: an isotope effect on electronic non-equilibrium quantum dynamics}, journal = {Physical Chemistry Chemical Physics}, year = {2021}, note = {Goncalves, Cayo E. M. Levine, R. D. Remacle, F.}, type = {Journal Article}, doi = {10.1039/d1cp01029h}, url = {https://pubs.rsc.org/en/content/articlepdf/2021/cp/d1cp01029h https://pubs.rsc.org/en/content/articlelanding/2021/CP/D1CP01029H}, author = {Goncalves, C. E. M. and Levine, R. D. and Remacle, F.} } @article {25592, title = {Room-Temperature Inter-Dot Coherent Dynamics in Multilayer Quantum Dot Materials}, journal = {Journal of Physical Chemistry C}, volume = {124}, number = {29}, year = {2020}, note = {Collini, Elisabetta Gattuso, Hugo Kolodny, Yuval Bolzonello, Luca Volpato, Andrea Fridman, Hanna T. Yochelis, Shira Mor, Morin Dehnel, Johanna Lifshitz, Efrat Paltiel, Yossi Levine, Raphael D. Remacle, Francoise}, pages = {16222-16231}, type = {Journal Article}, doi = {10.1021/acs.jpcc.0c05572}, author = {Collini, E. and Gattuso, H. and Kolodny, Y. and Bolzonello, L. and Volpato, A. and Fridman, H. T. and Yochelis, S. and Mor, M. and Dehnel, J. and E. Lifshitz and Paltiel, Y. and Levine, R. D. and Remacle, F.} } @article {25590, title = {Coherent Exciton Dynamics in Ensembles of Size-Dispersed CdSe Quantum Dot Dimers Probed via Ultrafast Spectroscopy: A Quantum Computational Study}, journal = {Applied Sciences-Basel}, volume = {10}, number = {4}, year = {2020}, note = {Gattuso, Hugo Fresch, Barbara Levine, Raphael D. Remacle, Francoise}, type = {Journal Article}, doi = {10.3390/app10041328}, author = {Gattuso, H. and Fresch, B. and Levine, R. D. and Remacle, F.} } @article {25585, title = {Correlated electron-nuclear motion during non-adiabatic transitions in LiH and its isotopomers}, journal = {Journal of Physics B-Atomic Molecular and Optical Physics}, volume = {53}, number = {13}, year = {2020}, note = {Komarova, Ksenia G. van den Wildenberg, Stephan Remacle, Francoise Levine, R. D.}, type = {Journal Article}, doi = {10.1088/1361-6455/ab84c7}, author = {Komarova, K. G. and van den Wildenberg, S. and Remacle, F. and Levine, R. D.} } @article {25589, title = {Massively parallel classical logic via coherent dynamics of an ensemble of quantum systems with dispersion in size}, journal = {Proceedings of the National Academy of Sciences of the United States of America}, volume = {117}, number = {35}, year = {2020}, note = {Gattuso, Hugo Levine, R. D. Remacle, F.}, pages = {21022-21030}, type = {Journal Article}, doi = {10.1073/pnas.2008170117}, url = {https://www.pnas.org/content/pnas/117/35/21022.full.pdf}, author = {Gattuso, H. and Levine, R. D. and Remacle, F.} } @article {25588, title = {Parallel Quantum Computation of Vibrational Dynamics}, journal = {Frontiers in Physics}, volume = {8}, year = {2020}, note = {Komarova, Ksenia Gattuso, Hugo Levine, R. D. Remacle, F.}, type = {Journal Article}, doi = {10.3389/fphy.2020.590699}, url = {https://fjfsdata01prod.blob.core.windows.net/articles/files/590699/pubmed-zip/.versions/3/.package-entries/fphy-08-590699.pdf?sv=2018-03-28\&sr=b\&sig=o0atRZAwXsSy7dyIauFVCS4EgTWHZrnZ4KyxG4UqWm8\%3D\&se=2021-05-31T10\%3A35\%3A29Z\&sp=r\&rscd=attachment\%3B\%20filen}, author = {Komarova, K. and Gattuso, H. and Levine, R. D. and Remacle, F.} } @article {25587, title = {Quantum Device Emulates the Dynamics of Two Coupled Oscillators}, journal = {Journal of Physical Chemistry Letters}, volume = {11}, number = {17}, year = {2020}, note = {Komarova, Ksenia Gattuso, Hugo Levine, R. D. Remade, F.}, pages = {6990-6995}, type = {Journal Article}, doi = {10.1021/acs.jpclett.0c01880}, author = {Komarova, K. and Gattuso, H. and Levine, R. D. and Remade, F.} } @article {25591, title = {Raman-guided subcellular pharmaco-metabolomics for metastatic melanoma cells}, journal = {Nature Communications}, volume = {11}, number = {1}, year = {2020}, note = {Du, Jiajun Su, Yapeng Qian, Chenxi Yuan, Dan Miao, Kun Lee, Dongkwan Ng, Alphonsus H. C. Wijker, Reto S. Ribas, Antoni Levine, Raphael D. Heath, James R. Wei, Lu}, type = {Journal Article}, doi = {10.1038/s41467-020-18376-x}, author = {Du, J. J. and Su, Y. P. and Qian, C. X. and Yuan, D. and Miao, K. and Lee, D. and Ng, A. H. C. and Wijker, R. S. and Ribas, A. and Levine, R. D. and Heath, J. R. and Wei, L.} } @article {25586, title = {Surprisal of a quantum state: Dynamics, compact representation, and coherence effects}, journal = {Journal of Chemical Physics}, volume = {153}, number = {21}, year = {2020}, note = {Komarova, K. Remacle, F. Levine, R. D.}, type = {Journal Article}, doi = {10.1063/5.0030272}, author = {Komarova, K. and Remacle, F. and Levine, R. D.} } @article {25584, title = {Thermodynamic energetics underlying genomic instability and whole-genome doubling in cancer}, journal = {Proceedings of the National Academy of Sciences of the United States of America}, volume = {117}, number = {31}, year = {2020}, note = {Remacle, Francoise Graeber, Thomas G. Levine, R. D.}, pages = {18880-18890}, type = {Journal Article}, doi = {10.1073/pnas.1920870117}, url = {https://www.pnas.org/content/pnas/117/31/18880.full.pdf}, author = {Remacle, F. and Graeber, T. G. and Levine, R. D.} } @article {25593, title = {Consecutive feedback-driven constitutional dynamic networks}, journal = {Proceedings of the National Academy of Sciences of the United States of America}, volume = {116}, number = {8}, year = {2019}, note = {Yue, Liang Wang, Shan Wulf, Verena Lilienthal, Sivan Remacle, Francoise Levine, R. D. Willner, Itamar}, pages = {2843-2848}, type = {Journal Article}, doi = {10.1073/pnas.1816670116}, url = {https://www.pnas.org/content/pnas/116/8/2843.full.pdf}, author = {Yue, L. and Wang, S. and Wulf, V. and Lilienthal, S. and Remacle, F. and Levine, R. D. and Willner, I.} } @article {25596, title = {Intracellular redox potential is correlated with miRNA expression in MCF7 cells under hypoxic conditions}, journal = {Proceedings of the National Academy of Sciences of the United States of America}, volume = {116}, number = {39}, year = {2019}, note = {Johnston, Hannah Dickinson, Paul Ivens, Alasdair Buck, Amy H. Levine, R. D. Remacle, Francoise Campbell, Colin J.}, pages = {19753-19759}, type = {Journal Article}, doi = {10.1073/pnas.1909455116}, url = {https://www.pnas.org/content/pnas/116/39/19753.full.pdf}, author = {Johnston, H. and Dickinson, P. and Ivens, A. and Buck, A. H. and Levine, R. D. and Remacle, F. and Campbell, C. J.} } @article {25597, title = {Metabolic, Physiological, and Transcriptomics Analysis of Batch Cultures of the Green Microalga Chlamydomonas Grown on Different Acetate Concentrations}, journal = {Cells}, volume = {8}, number = {11}, year = {2019}, note = {Bogaert, Kenny A. Perez, Emilie Rumin, Judith Giltay, Axel Carone, Michele Coosemans, Nadine Radoux, Michele Eppe, Gauthier Levine, Raphael D. Remacle, Francoise Remacle, Claire}, type = {Journal Article}, doi = {10.3390/cells8111367}, author = {Bogaert, K. A. and Perez, E. and Rumin, J. and Giltay, A. and Carone, M. and Coosemans, N. and Radoux, M. and Eppe, G. and Levine, R. D. and Remacle, F. and Remacle, C.} } @article {25594, title = {Temporal and spatially resolved imaging of the correlated nuclear-electronic dynamics and of the ionized photoelectron in a coherently electronically highly excited vibrating LiH molecule}, journal = {Journal of Chemical Physics}, volume = {151}, number = {13}, year = {2019}, note = {van den Wildenberg, Stephan Mignolet, Benoit Levine, R. D. Remacle, F.}, type = {Journal Article}, doi = {10.1063/1.5116250}, author = {van den Wildenberg, S. and Mignolet, B. and Levine, R. D. and Remacle, F.} } @article {25595, title = {Time resolved mechanism of the isotope selectivity in the ultrafast light induced dissociation in N-2}, journal = {Journal of Chemical Physics}, volume = {151}, number = {11}, year = {2019}, note = {Komarova, Ksenia G. Remade, Francoise Levine, R. D.}, type = {Journal Article}, doi = {10.1063/1.5118990}, author = {Komarova, K. G. and Remade, F. and Levine, R. D.} } @inbook {25605, title = {Attophotochemistry: Coherent Electronic Dynamics and Nuclear Motion}, booktitle = {Attosecond Molecular Dynamics}, series = {RSC Theoretical and Computational Chemistry Series}, volume = {13}, year = {2018}, note = {Ajay, J. S. Komarova, K. G. Van den Wildenberg, S. Remacle, F. Levine, R. D.}, pages = {308-347}, type = {Book Section}, author = {Ajay, J. S. and Komarova, K. G. and van den Wildenberg, S. and Remacle, F. and Levine, R. D.}, editor = {Vrakking, M. J. J. and Lepine, F.} } @article {25603, title = {Fast Energy Transfer in CdSe Quantum Dot Layered Structures: Controlling Coupling with Covalent-Bond Organic Linkers}, journal = {Journal of Physical Chemistry C}, volume = {122}, number = {10}, year = {2018}, note = {Cohen, Eyal Komm, Pavel Rosenthal-Strauss, Noa Dehnel, Joanna Lifshitz, Efrat Yochelis, Shira Levine, Raphael D. Remacle, Francoise Fresch, Barbara Marcus, Gilad Paltiel, Yossi}, pages = {5753-5758}, type = {Journal Article}, doi = {10.1021/acs.jpcc.7b11799}, author = {Cohen, E. and Komm, P. and Rosenthal-Strauss, N. and Dehnel, J. and E. Lifshitz and Yochelis, S. and Levine, R. D. and Remacle, F. and Fresch, B. and Marcus, G. and Paltiel, Y.} } @article {25602, title = {On the fly quantum dynamics of electronic and nuclear wave packets}, journal = {Chemical Physics Letters}, volume = {699}, year = {2018}, note = {Komarova, Ksenia G. Remacle, F. Levine, R. D.}, pages = {155-161}, type = {Journal Article}, doi = {10.1016/j.cplett.2018.03.050}, author = {Komarova, K. G. and Remacle, F. and Levine, R. D.} } @article {25604, title = {Surprisal analysis of genome-wide transcript profiling identifies differentially expressed genes and pathways associated with four growth conditions in the microalga Chlamydomonas}, journal = {Plos One}, volume = {13}, number = {4}, year = {2018}, note = {Bogaert, Kenny A. Manoharan-Basil, Sheeba S. Perez, Emilie Levine, Raphael D. Remacle, Francoise Remacle, Claire}, type = {Journal Article}, doi = {10.1371/journal.pone.0195142}, url = {https://storage.googleapis.com/plos-corpus-prod/10.1371/journal.pone.0195142/1/pone.0195142.pdf?X-Goog-Algorithm=GOOG4-RSA-SHA256\&X-Goog-Credential=wombat-sa\%40plos-prod.iam.gserviceaccount.com\%2F20210531\%2Fauto\%2Fstorage\%2Fgoog4_request\&X-Goog-Date=20210}, author = {Bogaert, K. A. and Manoharan-Basil, S. S. and Perez, E. and Levine, R. D. and Remacle, F. and Remacle, C.} } @article {25606, title = {Time-dependent view of an isotope effect in electron-nuclear nonequilibrium dynamics with applications to N-2}, journal = {Proceedings of the National Academy of Sciences of the United States of America}, volume = {115}, number = {23}, year = {2018}, note = {Ajay, Jayanth S. Komarova, Ksenia G. Remacle, Francoise Levine, R. D.}, pages = {5890-5895}, type = {Journal Article}, doi = {10.1073/pnas.1804455115}, url = {https://www.pnas.org/content/pnas/115/23/5890.full.pdf}, author = {Ajay, J. S. and Komarova, K. G. and Remacle, F. and Levine, R. D.} } @inbook {25600, title = {Addressing the Challenge of Molecular Change: An Interim Report}, booktitle = {Annual Review of Physical Chemistry, Vol 69}, series = {Annual Review of Physical Chemistry}, volume = {69}, year = {2018}, note = {Levine, Raphael D.}, pages = {1-21}, type = {Book Section}, doi = {10.1146/annurev-physchem-102717-010036}, author = {Levine, R. D.}, editor = {Johnson, M.A. and Martinez, T. J.} } @article {25598, title = {Intercommunication of DNA-Based Constitutional Dynamic Networks}, journal = {Journal of the American Chemical Society}, volume = {140}, number = {28}, year = {2018}, note = {Yue, Liang Wang, Shan Lilienthal, Sivan Wulf, Verena Remacle, Francoise Levine, R. D. Willner, Itamar}, pages = {8721-8731}, type = {Journal Article}, doi = {10.1021/jacs.8b03450}, author = {Yue, L. and Wang, S. and Lilienthal, S. and Wulf, V. and Remacle, F. and Levine, R. D. and Willner, I.} } @article {25599, title = {Personalized disease signatures through information-theoretic compaction of big cancer data}, journal = {Proceedings of the National Academy of Sciences of the United States of America}, volume = {115}, number = {30}, year = {2018}, note = {Vasudevan, Swetha Flashner-Abramson, Efrat Remacle, F. Levine, R. D. Kravchenko-Balasha, Nataly}, pages = {7694-7699}, type = {Journal Article}, doi = {10.1073/pnas.1804214115}, url = {https://www.pnas.org/content/pnas/115/30/7694.full.pdf}, author = {Vasudevan, S. and Flashner-Abramson, E. and Remacle, F. and Levine, R. D. and Kravchenko-Balasha, N.} } @article {25601, title = {Propagation of nonstationary electronic and nuclear states: attosecond dynamics in LiF}, journal = {Molecular Physics}, volume = {116}, number = {19-20}, year = {2018}, note = {Komarova, Ksenia G. Remacle, F. Levine, R. D. SI}, pages = {2524-2532}, type = {Journal Article}, doi = {10.1080/00268976.2018.1451932}, author = {Komarova, K. G. and Remacle, F. and Levine, R. D.} } @article {25616, title = {Coherent electronic and nuclear dynamics in a rhodamine heterodimer-DNA supramolecular complex}, journal = {Physical Chemistry Chemical Physics}, volume = {19}, number = {34}, year = {2017}, note = {Cipolloni, M. Fresch, B. Occhiuto, I. Rukin, P. Komarova, K. G. Cecconello, A. Willner, I. Levine, R. D. Remacle, F. Collini, E.}, pages = {23043-23051}, type = {Journal Article}, doi = {10.1039/c7cp01334e}, url = {https://pubs.rsc.org/en/content/articlepdf/2017/cp/c7cp01334e}, author = {Cipolloni, M. and Fresch, B. and Occhiuto, I. and Rukin, P. and Komarova, K. G. and Cecconello, A. and Willner, I. and Levine, R. D. and Remacle, F. and Collini, E.} } @article {25614, title = {Implementation of Multivariable Logic Functions in Parallel by Electrically Addressing a Molecule of Three Dopants in Silicon}, journal = {Chemphyschem}, volume = {18}, number = {13}, year = {2017}, note = {Fresch, Barbara Bocquel, Juanita Hiluf, Dawit Rogge, Sven Levine, Raphael D. Remacle, Francoise SI}, pages = {1790-1797}, type = {Journal Article}, doi = {10.1002/cphc.201700222}, author = {Fresch, B. and Bocquel, J. and Hiluf, D. and Rogge, S. and Levine, R. D. and Remacle, F.} } @article {25612, title = {Implementation of Probabilistic Algorithms by Multi-chromophoric Molecular Networks with Application to Multiple Travelling Pathways}, journal = {Chemphyschem}, volume = {18}, number = {13}, year = {2017}, note = {Fresch, Barbara Remacle, Francoise Levine, Raphael D. SI}, pages = {1782-1789}, type = {Journal Article}, doi = {10.1002/cphc.201700228}, author = {Fresch, B. and Remacle, F. and Levine, R. D.} } @article {25613, title = {A Probabilistic Finite State Logic Machine Realized Experimentally on a Single Dopant Atom}, journal = {Nano Letters}, volume = {17}, number = {3}, year = {2017}, note = {Fresch, Barbara Bocquel, Juanita Rogge, Sven Levine, R. D. Remacle, F.}, pages = {1846-1852}, type = {Journal Article}, doi = {10.1021/acs.nanolett.6b05149}, author = {Fresch, B. and Bocquel, J. and Rogge, S. and Levine, R. D. and Remacle, F.} } @article {25615, title = {Understanding cancer phenomena using a thermodynamic-based approach}, journal = {European Biophysics Journal with Biophysics Letters}, volume = {46}, year = {2017}, note = {Flashner-Abramson, E. Heath, J. R. Levine, R. D. Kravchenko-Balasha, N. 1}, pages = {S274-S274}, type = {Journal Article}, author = {Flashner-Abramson, E. and Heath, J. R. and Levine, R. D. and Kravchenko-Balasha, N.} } @inbook {25609, title = {Controlling Coherent Quantum Nuclear Dynamics in LiH by Ultra Short IR Atto Pulses}, booktitle = {Progress in Ultrafast Intense Laser Science Xiii}, series = {Springer Series in Chemical Physics}, volume = {116}, year = {2017}, note = {Nikodem, Astrid Levine, R. D. Remacle, F.}, pages = {41-65}, type = {Book Section}, doi = {10.1007/978-3-319-64840-8_3}, author = {Nikodem, A. and Levine, R. D. and Remacle, F.}, editor = {Yamanouchi, K. and Hill, W. T. and Paulus, G. G.} } @article {25608, title = {Nuclear Motion Driven Ultrafast Photodissociative Charge Transfer of the PENNA Cation: An Experimental and Computational Study}, journal = {Journal of Physical Chemistry A}, volume = {121}, number = {7}, year = {2017}, note = {Sun, Shoutian Mignolet, Benoit Fan, Lin Li, Wen Levine, Raphael D. Remacle, Francoise}, pages = {1442-1447}, type = {Journal Article}, doi = {10.1021/acs.jpca.6b12310}, author = {Sun, S. T. and Mignolet, B. and Fan, L. and Li, W. and Levine, R. D. and Remacle, F.} } @article {25611, title = {Photochemistry of highly excited states}, journal = {Proceedings of the National Academy of Sciences of the United States of America}, volume = {114}, number = {52}, year = {2017}, note = {Levine, R. D.}, pages = {13594-13596}, type = {Journal Article}, doi = {10.1073/pnas.1718814114}, url = {https://www.pnas.org/content/pnas/114/52/13594.full.pdf}, author = {Levine, R. D.} } @article {25607, title = {Pumping and probing vibrational modulated coupled electronic coherence in HCN using short UV fs laser pulses: a 2D quantum nuclear dynamical study}, journal = {Physical Chemistry Chemical Physics}, volume = {19}, number = {30}, year = {2017}, note = {van den Wildenberg, S. Mignolet, B. Levine, R. D. Remacle, F.}, pages = {19837-19846}, type = {Journal Article}, doi = {10.1039/c7cp02048a}, url = {https://pubs.rsc.org/en/content/articlepdf/2017/cp/c7cp02048a}, author = {van den Wildenberg, S. and Mignolet, B. and Levine, R. D. and Remacle, F.} } @article {25610, title = {Spatial and temporal control of populations, branching ratios, and electronic coherences in LiH by a single one-cycle infrared pulse}, journal = {Physical Review A}, volume = {95}, number = {5}, year = {2017}, note = {Nikodem, Astrid Levine, R. D. Remacle, F.}, type = {Journal Article}, doi = {10.1103/PhysRevA.95.053404}, url = {https://journals.aps.org/pra/pdf/10.1103/PhysRevA.95.053404}, author = {Nikodem, A. and Levine, R. D. and Remacle, F.} } @article {13087, title = {Continuous variables logic via coupled automata using a DNAzyme cascade with feedback}, journal = {Chemical Science}, year = {2017}, publisher = {Royal Society of Chemistry}, author = {Lilienthal, S and Klein, M. and Orbach, R and WILLNER, I and Remacle, F. and LEVINE, RD} } @article {13089, title = {Multivariate Surprisal Analysis of Gene Expression Levels}, journal = {Entropy}, volume = {18}, number = {12}, year = {2016}, pages = {445}, publisher = {Multidisciplinary Digital Publishing Institute}, author = {Remacle, Francoise and Goldstein, Andrew S and Levine, Raphael D.} } @article {13088, title = {Controlling coherent quantum nuclear dynamics in LiH by ultra short IR atto pulses}, journal = {Progress in Ultrafast Laser Science XIII}, year = {2016}, pages = {in press}, publisher = {Springer}, author = {Nikodem, Astrid and LEVINE, RD and Remacle, Fran{\c c}oise and K Yamanouchi and W Hill and Paulus, FG} } @inbook {13085, title = {Controlling Coherent Quantum Nuclear Dynamics in LiH by Ultra Short IR Atto Pulses}, booktitle = {Ultrafast Laser Science XIII}, year = {2016}, publisher = {Springer}, organization = {Springer}, address = {Dordrecht}, author = {A. Nikodem and LEVINE, RD and Remacle, F.}, editor = {K Yamanouchi and W Hill and F Paulus} } @inbook {12347, title = {Electronic and Nuclear Dynamics for a Non- Equilibrium Electronic State: the Ultrafast Pumping of N2}, year = {2016}, publisher = {Springer}, organization = {Springer}, address = { Dordrecht}, author = {J. {\v S}mydke and S. A. Jayanth and Remacle, F. and LEVINE, RD}, editor = {J. Maruani} } @article {12265, title = {Microfluidic Chip with molecular beacons}, journal = {RNA \& Disease}, volume = {3}, year = {2016}, pages = {e1183}, author = {S. Zadran and Remacle, F. and LEVINE, RD} } @article { ISI:000372508600003, title = {Critical Points in Tumorigenesis: A Carcinogen-Initiated Phase Transition Analyzed via Single-Cell Proteomics}, journal = {SMALL}, volume = {12}, year = {2016}, month = {MAR 16}, pages = {1425-1431}, issn = {1613-6810}, doi = {10.1002/smll.201501178}, author = {Poovathingal, Suresh Kumar and Kravchenko-Balasha, Nataly and Shin, Young Shik and Levine, Raphael David and Heath, James R.} } @article { ISI:000375977600029, title = {Intercellular signaling through secreted proteins induces free-energy gradient-directed cell movement}, journal = {PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA}, volume = {113}, year = {2016}, month = {MAY 17}, pages = {5520-5525}, abstract = {Controlling cell migration is important in tissue engineering and medicine. Cell motility depends on factors such as nutrient concentration gradients and soluble factor signaling. In particular, cell-cell signaling can depend on cell-cell separation distance and can influence cellular arrangements in bulk cultures. Here, we seek a physical-based approach, which identifies a potential governed by cell-cell signaling that induces a directed cell-cell motion. A single-cell barcode chip (SCBC) was used to experimentally interrogate secreted proteins in hundreds of isolated glioblastoma brain cancer cell pairs and to monitor their relative motions over time. We used these trajectories to identify a range of cell-cell separation distances where the signaling was most stable. We then used a thermodynamics-motivated analysis of secreted protein levels to characterize free-energy changes for different cell-cell distances. We show that glioblastoma cell-cell movement can be described as Brownian motion biased by cell-cell potential. To demonstrate that the free-energy potential as determined by the signaling is the driver of motion, we inhibited two proteins most involved in maintaining the free-energy gradient. Following inhibition, cell pairs showed an essentially random Brownian motion, similar to the case for untreated, isolated single cells.}, issn = {0027-8424}, doi = {10.1073/pnas.1602171113}, author = {Kravchenko-Balasha, Nataly and Shin, Young Shik and Sutherland, Alex and LEVINE, RD and Heath, James R.} } @article { ISI:000376417300043, title = {Probing in Space and Time the Nuclear Motion Driven by Nonequilibrium Electronic Dynamics in Ultrafast Pumped N-2}, journal = {JOURNAL OF PHYSICAL CHEMISTRY A}, volume = {120}, year = {2016}, month = {MAY 19}, pages = {3335-3342}, abstract = {An Ultrafast electronic excitation of N-2 in the vacuum ultraviolet creates a nonstationary coherent linear superposition of interacting valence and Rydberg states resulting in a net oscillating dipole moment. There is therefore a linear response to an electrical field that can be queried by varying the time delay between the pump and a second optical probe pulse. Both the pump and probe pulses are included in our computation as part of the Hamiltonian, and the time dependent wave function for both electronic and nuclear dynamics is computed using a grid representation for the internuclear coordinate. Even on an ultrafast time scale there are several processes that can be discerned beyond the expected coherence oscillations. In particular, the coupling between the excited valence and Rydberg states of the same symmetry is very evident and can be directly probed by varying the delay between pulse and. probe. For quite a number of vibrations the nuclear motion does not dephase the electronic disequilibrium. However, the nuclear motion does modulate the dipolar response by taking the wave packet in and out of the Franck-Condon region and by its strong influence on the coupling of the Rydberg and valence states. A distinct isotope effect arises from the dependence of the interstate coupling on the nuclear mass.}, issn = {1089-5639}, doi = {10.1021/acs.jpca.6b00165}, author = {Ajay, J. and Smydke, J. and Remacle, F. and LEVINE, RD} } @article { ISI:000376417300044, title = {Quantum Nuclear Dynamics Pumped and Probed by Ultrafast Polarization Controlled Steering of a Coherent Electronic State in LiH}, journal = {JOURNAL OF PHYSICAL CHEMISTRY A}, volume = {120}, year = {2016}, month = {MAY 19}, pages = {3343-3352}, abstract = {The quantum wave packet dynamics following a coherent electronic excitation of LiH by an ultrashort, polarized, strong one cycle infrared optical pulse is computed on several electronic states using a grid method. The coupling to the strong field of the pump and the probe pulses is included in the Hamiltonian used to solve the time-dependent Schrodinger equation. The polarization of the pump pulse allows us to control the localization in time and in space of the nonequilibrium coherent electronic motion and the subsequent nuclear dynamics. We show that transient absorption, resulting from the interaction of the total molecular dipole with the electric fields of the pump and the probe, is a very versatile probe of the different time scales of the vibronic dynamics. It allows probing both the ultrashort, femtosecond time scale of the electronic coherences as well as the longer dozens of femtoseconds time scales of the nuclear motion on the excited electronic states. The ultrafast beatings of the electronic coherences in space and in time are shown to be modulated by the different periods of the nuclear motion.}, issn = {1089-5639}, doi = {10.1021/acs.jpca.6b00140}, author = {Nikodem, Astrid and LEVINE, RD and Remacle, F.} } @article { ISI:000379457200024, title = {A Thermodynamic-Based Interpretation of Protein Expression Heterogeneity in Different Glioblastoma Multiforme Tumors Identifies Tumor-Specific Unbalanced Processes}, journal = {JOURNAL OF PHYSICAL CHEMISTRY B}, volume = {120}, year = {2016}, month = {JUL 7}, pages = {5990-5997}, abstract = {We describe a thermodynamic-motivated, information theoretic analysis of proteomic data collected from a series of 8 glioblastoma multiforme (GBM) tumors. GBMs are considered here as prototypes of heterogeneous cancers. That heterogeneity is viewed here as manifesting in different unbalanced biological processes that are associated with thermodynamic-like constraints. The analysis yields a molecular description of a stable steady state that is common across all tumors. It also resolves molecular descriptions of unbalanced processes that are shared by several tumors, such as hyperactivated phosphoprotein signaling networks. Further, it resolves unbalanced processes that provide unique classifiers of tumor subgroups. The results of the theoretical interpretation are compared against those of statistical multivariate methods and are shown to provide a superior level of resolution for identifying unbalanced processes in GBM tumors. The identification of specific constraints for each GBM tumor suggests tumor-specific combination therapies that may reverse this imbalance.}, issn = {1520-6106}, doi = {10.1021/acs.jpcb.6b01692}, author = {Kravchenko-Balasha, Nataly and Johnson, Hannah and White, Forest M. and Heath, James R. and LEVINE, RD} } @article { ISI:000381151200013, title = {Operation of a quantum dot in the finite-state machine mode: Single-electron dynamic memory}, journal = {JOURNAL OF APPLIED PHYSICS}, volume = {120}, year = {2016}, month = {JUL 14}, abstract = {A single electron dynamic memory is designed based on the non-equilibrium dynamics of charge states in electrostatically defined metallic quantum dots. Using the orthodox theory for computing the transfer rates and a master equation, we model the dynamical response of devices consisting of a charge sensor coupled to either a single and or a double quantum dot subjected to a pulsed gate voltage. We show that transition rates between charge states in metallic quantum dots are characterized by an asymmetry that can be controlled by the gate voltage. This effect is more pronounced when the switching between charge states corresponds to a Markovian process involving electron transport through a chain of several quantum dots. By simulating the dynamics of electron transport we demonstrate that the quantum box operates as a finite-state machine that can be addressed by choosing suitable shapes and switching rates of the gate pulses. We further show that writing times in the ns range and retention memory times six orders of magnitude longer, in the ms range, can be achieved on the double quantum dot system using experimentally feasible parameters, thereby demonstrating that the device can operate as a dynamic single electron memory. Published by AIP Publishing.}, issn = {0021-8979}, doi = {10.1063/1.4955422}, author = {Klymenko, M. V. and Klein, M. and LEVINE, RD and Remacle, F.} } @article { ISI:000351735600003, title = {Coherent Electronic Wave Packet Motion in C-60 Controlled by the Waveform and Polarization of Few-Cycle Laser Fields}, journal = {PHYSICAL REVIEW LETTERS}, volume = {114}, year = {2015}, month = {MAR 27}, abstract = {Strong laser fields can be used to trigger an ultrafast molecular response that involves electronic excitation and ionization dynamics. Here, we report on the experimental control of the spatial localization of the electronic excitation in the C-60 fullerene exerted by an intense few-cycle (4 fs) pulse at 720 nm. The control is achieved by tailoring the carrier-envelope phase and the polarization of the laser pulse. We find that the maxima and minima of the photoemission-asymmetry parameter along the laser-polarization axis are synchronized with the localization of the coherent electronic wave packet at around the time of ionization.}, issn = {0031-9007}, doi = {10.1103/PhysRevLett.114.123004}, author = {Li, H. and Mignolet, B. and Wachter, G. and Skruszewicz, S. and Zherebtsov, S. and Suessmann, F. and Kessel, A. and Trushin, S. A. and Kling, Nora G. and Kuebel, M. and Ahn, B. and Kim, D. and Ben-Itzhak, I. and Cocke, C. L. and Fennel, T. and Tiggesbaeumker, J. and Meiwes-Broer, K. -H. and Lemell, C. and Burgdoerfer, J. and LEVINE, RD and Remacle, F. and Kling, M. F.} } @article { ISI:000348147100054, title = {Ternary DNA computing using 3 x 3 multiplication matrices}, journal = {CHEMICAL SCIENCE}, volume = {6}, year = {2015}, pages = {1288-1292}, abstract = {Non-Boolean computations implementing operations on multi-valued variables beyond base 2 allow enhanced computational complexity. We introduce DNA as a functional material for ternary computing, and in particular demonstrate the use of three-valued oligonucleotide inputs to construct a 3 x 3 multiplication table. The system consists of two three-valued inputs of -1; 0; + 1 and a fluorophore/quencher functional hairpin acting as computational and reporter module. The interaction of the computational hairpin module with the different values of the inputs yields a 3 x 3 multiplication matrix consisting of nine nanostructures that are read out by three distinct fluorescence intensities. By combining three different hairpin computational modules, each modified with a different fluorophore/quencher pair, and using different sets of inputs, the parallel operation of three multiplication tables is demonstrated.}, issn = {2041-6520}, doi = {10.1039/c4sc02930e}, author = {Orbach, Ron and Lilienthal, Sivan and Klein, Michael and LEVINE, RD and Remacle, Francoise and Willner, Itamar} } @article { ISI:000359799600008, title = {Information processing in parallel through directionally resolved molecular polarization components in coherent multidimensional spectroscopy}, journal = {JOURNAL OF CHEMICAL PHYSICS}, volume = {143}, year = {2015}, month = {AUG 14}, abstract = {We propose that information processing can be implemented by measuring the directional components of the macroscopic polarization of an ensemble of molecules subject to a sequence of laser pulses. We describe the logic operation theoretically and demonstrate it by simulations. The measurement of integrated stimulated emission in different phase matching spatial directions provides a logic decomposition of a function that is the discrete analog of an integral transform. The logic operation is reversible and all the possible outputs are computed in parallel for all sets of possible multivalued inputs. The number of logic variables of the function is the number of laser pulses used in sequence. The logic function that is computed depends on the chosen chromophoric molecular complex and on its interactions with the solvent and on the two time intervals between the three pulses and the pulse strengths and polarizations. The outputs are the homodyne detected values of the polarization components that are measured in the allowed phase matching macroscopic directions, k(l), k(l) = Sigma(i) l(i) k(i) where k(i) is the propagation direction of the ith pulse and \l(i)\ is a set of integers that encodes the multivalued inputs. Parallelism is inherently implemented because all the partial polarizations that define the outputs are processed simultaneously. The outputs, which are read directly on the macroscopic level, can be multivalued because the high dynamical range of partial polarization measurements by nonlinear coherent spectroscopy allows for fine binning of the signals. The outputs are uniquely related to the inputs so that the logic is reversible. (C) 2015 AIP Publishing LLC.}, issn = {0021-9606}, doi = {10.1063/1.4928066}, author = {Yan, Tian-Min and Fresch, Barbara and LEVINE, RD and Remacle, F.} } @article { ISI:000365079800004, title = {Metabolomic analysis of the green microalga Chlamydomonas reinhardtii cultivated under day/night conditions}, journal = {JOURNAL OF BIOTECHNOLOGY}, volume = {215}, year = {2015}, month = {DEC 10}, pages = {20-26}, abstract = {Biomass composition of Chlamydomonas reinhardtii was studied during two consecutive cycles of 12 h light/12 h dark. As in our experimental conditions the two synchronized divisions were separated by 20 h, it was possible to show that accumulation of dry weight, proteins, chlorophyll and fatty acids mainly depends on cell division, whereas starch accumulation depends on a circadian rhythm as reported previously. Our metabolomics analyses also revealed that accumulation of five (Ser, Val, Leu, Ile and Thr) of the nine free amino acids detected displayed rhythmicity, depending on cell division while Glu was 20-50 times more abundant than the other ones probably because this free amino acid serves not only for protein synthesis but also for biosynthesis of nitrogen compounds. In addition, we performed a thermodynamic-motivated theoretical approach known as {\textquoteleft}surprisal analysis{\textquoteright}. The results from this analysis showed that cells were close to a steady state all along the 48 h of the experiment. In addition, calculation of free energy of cellular metabolites showed that the transition point, i.e. the state which immediately precedes cell division, corresponds to the most unstable stage of the cell cycle and that division is identified as the greatest drop in the free energy of metabolites. (C) 2015 Elsevier B.V. All rights reserved.}, issn = {0168-1656}, doi = {10.1016/j.jbiotec.2015.04.012}, author = {Willamme, Remi and Alsafra, Zouheir and Arumugam, Rameshkumar and Eppe, Gauthier and Remacle, Francoise and LEVINE, RD and Remacle, Claire} } @article { ISI:000355014900037, title = {Parallel and Multivalued Logic by the Two-Dimensional Photon-Echo Response of a Rhodamine-DNA Complex}, journal = {JOURNAL OF PHYSICAL CHEMISTRY LETTERS}, volume = {6}, year = {2015}, month = {MAY 7}, pages = {1714-1718}, abstract = {Implementing parallel and multivalued logic operations at the molecular scale has the potential to improve the miniaturization and efficiency of a new generation of nanoscale computing devices. Two-dimensional photon-echo spectroscopy is capable of resolving dynamical pathways on electronic and vibrational molecular states. We experimentally demonstrate the implementation of molecular decision trees, logic operations where all possible values of inputs are processed in parallel and the outputs are read simultaneously, by probing the laser induced dynamics of populations and coherences in a rhodamine dye mounted on a short DNA duplex. The inputs are provided by the bilinear interactions between the molecule and the laser pulses, and the output values are read from the two-dimensional molecular response at specific frequencies. Our results highlights how ultrafast dynamics between multiple molecular states induced by light-matter interactions can be used as an advantage for performing complex logic operations in parallel, operations that are faster than electrical switching.}, issn = {1948-7185}, doi = {10.1021/acs.jpclett.5b00514}, author = {Fresch, Barbara and Cipolloni, Marco and Yan, Tian-Min and Collini, Elisabetta and LEVINE, RD and Remacle, F.} } @article { ISI:000363952200011, title = {Statistical thermodynamics of transcription profiles in normal development and tumorigeneses in cohorts of patients}, journal = {EUROPEAN BIOPHYSICS JOURNAL WITH BIOPHYSICS LETTERS}, volume = {44}, year = {2015}, month = {DEC}, pages = {709-726}, abstract = {Experimental biology is providing the distribution of numerous different biological molecules inside cells and in body fluids of patients. Statistical methods of analysis have very successfully examined these rather large databases. We seek to use a thermodynamic analysis to provide a physical understanding and quantitative characterization of human cancers and other pathologies within a molecule-centered approach. The key technical development is the introduction of a Lagrangian. By imposing constraints the minimal value of the Lagrangian defines a thermodynamically stable state of the cellular system. The minimization also allows using experimental data measured at a number of different conditions to evaluate the steady-state distribution of biomolecules such as messenger RNAs. Thereby the number of effectively accessible quantum states of biomolecules is determined from the experimentally measured expression levels. With the increased resolution provided by the minimization of the Lagrangian one can differentiate between normal and diseased patients and further between disease subtypes. Each such refinement corresponds to imposing an additional constraint of biological origin. The constraints are the unbalanced ongoing biological processes in the system. MicroRNA expression level data for control and diseased lung cancer patients are analyzed as an example.}, issn = {0175-7571}, doi = {10.1007/s00249-015-1069-y}, author = {Remacle, F. and LEVINE, RD} } @article {13086, title = {Surprisal Analysis of Glioblastoma Multiform (GBM) MicroRNA Dynamics Unveils Tumor Specific Phenotype}, journal = {PlosOne}, volume = {9}, number = {e10171}, year = {2014}, author = {S. Zadran and Remacle, F. and LEVINE, RD} } @article { ISI:000332224100001, title = {Control of electronic dynamics visualized by angularly resolved photoelectron spectra: A dynamical simulation with an IR pump and XUV attosecond-pulse-train probe}, journal = {PHYSICAL REVIEW A}, volume = {89}, year = {2014}, month = {FEB 13}, abstract = {A dynamical simulation via a coupled-equation scheme that includes the ionization continua and field-induced effects describes a pump-probe experiment that monitors ultrafast electronic dynamics in LiH. The ionizing XUV attosecond pulse train that is included in the simulation is used as a frequency filter. By tuning the time interval between the attosecond pulses of the train to a beating frequency of the wave packet induced by the IR pump pulse we characterize the changing spatial localization from one end of the molecule to the other, reflecting the interferences of the nonstationary electronic density.}, issn = {2469-9926}, doi = {10.1103/PhysRevA.89.021403}, author = {Mignolet, B. and LEVINE, RD and Remacle, F.} } @article { ISI:000332189900027, title = {DNAzyme-based 2:1 and 4:1 multiplexers and 1:2 demultiplexer}, journal = {CHEMICAL SCIENCE}, volume = {5}, year = {2014}, month = {MAR}, pages = {1074-1081}, abstract = {Scaffolding proteins play a central role in many regulatory cellular networks, where signalling proteins trigger different, and even orthogonal biological pathways. Such biological regulatory networks can be duplicated by multiplexer/demultiplexer logic operations. We present the use of libraries of Mg2+-dependent DNAzyme subunits as computational moduli for the construction of 2:1 and 4:1 multiplexers and a 1:2 demultiplexer. In the presence of the appropriate inputs, and the presence or absence of selector units, the guided assembly of the DNAzyme subunits to form active Mg2+-dependent DNAzyme proceeds. The formation of the active DNAzyme nanostructures is controlled by the energetics associated with the resulting duplexes between the inputs/selectors and the DNAzyme subunits. The library subunits are designed in such a way that, in the presence of the appropriate inputs/selectors, the inputs are knocked-down or triggered-on to yield the respective multiplexer/demultiplexer operations. Fluorescence is used as the readout for the outputs of the logic operations. The DNAzyme-based multiplexer/demultiplexer systems present biomolecular assemblies for data compression and decompression.}, issn = {2041-6520}, doi = {10.1039/c3sc52752b}, author = {Orbach, Ron and Remacle, Francoise and LEVINE, RD and Willner, Itamar} } @article { ISI:000335199000090, title = {Glioblastoma cellular architectures are predicted through the characterization of two-cell interactions}, journal = {PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA}, volume = {111}, year = {2014}, month = {APR 29}, pages = {6521-6526}, abstract = {To understand how pairwise cellular interactions influence cellular architectures, we measured the levels of functional proteins associated with EGF receptor (EGFR) signaling in pairs of U87EGFR variant III oncogene receptor cells (U87EGFRvIII) at varying cell separations. Using a thermodynamics-derived approach we analyzed the cell-separation dependence of the signaling stability, and identified that the stable steady state of EGFR signaling exists when two U87EGFRvIII cells are separated by 80-100 mu m. This distance range was verified as the characteristic intercellular separation within bulk cell cultures. EGFR protein network signaling coordination for the U87EGFRvIII system was lowest at the stable state and most similar to isolated cell signaling. Measurements of cultures of less tumorigenic U87PTEN cells were then used to correctly predict that stable EGFR signaling occurs for those cells at smaller cell-cell separations. The intimate relationship between functional protein levels and cellular architectures explains the scattered nature of U87EGFRvIII cells relative to U87PTEN cells in glioblastoma multiforme tumors.}, issn = {0027-8424}, doi = {10.1073/pnas.1404462111}, author = {Kravchenko-Balasha, Nataly and Wang, Jun and Remacle, Francoise and LEVINE, RD and Heath, James R.} } @article { ISI:000335515200009, title = {AttoPhotoChemistry. Probing ultrafast electron dynamics by the induced nuclear motion: The prompt and delayed predissociation of N-2}, journal = {CHEMICAL PHYSICS LETTERS}, volume = {601}, year = {2014}, month = {MAY 9}, pages = {45-48}, abstract = {Quantum mechanical wavepacket dynamics simulation that includes the nuclear motion exhibit a prompt, few fs, dissociation of electronically attosecond excited N-2 in addition to the slow dissociation evident from spectral line broadening in well resolved spectra. The simulations show that nuclear motion can probe early times electron dynamics. The separation of time scales is mimicked by a model study fashioned like chemical kinetics of unimolecular dissociation. The physical origin of the separation into prompt and delayed decay is argued to be the same in the vibrational and the present case, namely that there are more bound than dissociative channels. (C) 2014 Published by Elsevier B.V.}, issn = {0009-2614}, doi = {10.1016/j.cplett.2014.03.031}, author = {Muskatel, B. H. and Remacle, F. and LEVINE, RD} } @article { ISI:000337721200012, title = {Charge migration in the bifunctional PENNA cation induced and probed by ultrafast ionization: a dynamical study}, journal = {JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS}, volume = {47}, year = {2014}, month = {JUN 28}, abstract = {A full dynamical simulation shows that the charge transfer between the amine and the phenyl moieties of the cation of the bifunctional molecule 2-phenylethyl-N,N-dimethylamine can be induced and subsequently probed by two ultrashort photoionizations. The first ionization of the pump-probe scheme is by a 1.5 fs UV or 6 fs IR pulse that ionizes the neutral. The pump pulse can be tailored to produce a coherent superposition of the electronic states of the cation that differ in their energy and spatial localization of their electron density. The time-dependent amplitudes of the states of the superposition means that the state of the cation is not stationary and we show that it is beating between the two ends of the molecule. This beating is next probed by a second attosecond XUV pulse. The ultrafast photoionization of the cation to the dication probes the spatial charge reorganization in the cation. We use the computed time-dependent molecular frame photoelectron angular distributions as a quantitative measure of the charge migration. The computation of the dynamics are carried out by a coupled equation scheme that includes an electronic manifold for the three charge states: neutral, cation and dication, the coupling to the ionization continua of the cation and the dication and the dynamics induced by the pump and the probe pulses.}, issn = {0953-4075}, doi = {10.1088/0953-4075/47/12/124011}, author = {Mignolet, B. and LEVINE, RD and Remacle, F.} } @article { ISI:000347121300003, title = {Computational Surprisal Analysis Speeds-Up Genomic Characterization of Cancer Processes}, journal = {PLOS ONE}, volume = {9}, year = {2014}, month = {NOV 18}, abstract = {Surprisal analysis is increasingly being applied for the examination of transcription levels in cellular processes, towards revealing inner network structures and predicting response. But to achieve its full potential, surprisal analysis should be integrated into a wider range computational tool. The purposes of this paper are to combine surprisal analysis with other important computation procedures, such as easy manipulation of the analysis results - e.g. to choose desirable result subsets for further inspection -, retrieval and comparison with relevant datasets from public databases, and flexible graphical displays for heuristic thinking. The whole set of computation procedures integrated into a single practical tool is what we call Computational Surprisal Analysis. This combined kind of analysis should facilitate significantly quantitative understanding of different cellular processes for researchers, including applications in proteomics and metabolomics. Beyond that, our vision is that Computational Surprisal Analysis has the potential to reach the status of a routine method of analysis for practitioners. The resolving power of Computational Surprisal Analysis is here demonstrated by its application to a variety of cellular cancer process transcription datasets, ours and from the literature. The results provide a compact biological picture of the thermodynamic significance of the leading gene expression phenotypes in every stage of the disease. For each transcript we characterize both its inherent steady state weight, its correlation with the other transcripts and its variation due to the disease. We present a dedicated website to facilitate the analysis for researchers and practitioners.}, issn = {1932-6203}, doi = {10.1371/journal.pone.0108549}, author = {Kravchenko-Balasha, Nataly and Simon, Simcha and LEVINE, RD and Remacle, F. and Exman, Iaakov} } @article { ISI:000340808300049, title = {Electronic Dynamics by Ultrafast Pump Photoelectron Detachment Probed by Ionization: A Dynamical Simulation of Negative-Neutral-Positive in LiH-}, journal = {JOURNAL OF PHYSICAL CHEMISTRY A}, volume = {118}, year = {2014}, month = {AUG 21}, pages = {6721-6729}, abstract = {The control of electronic dynamics in the neutral electronic states of LiH before the onset of significant nuclei motion is investigated using a negative-neutral-positive (NeNePo) ultrafast IR pump-attoescond pulse train (APT) probe scheme. Starting from the ground state of the anion (LiH-), multiphoton ultrafast electron detachment and subsequent excitation of the neutral by a few femtosecond intense IR pulse produces a non-equilibrium electronic density in neutral LiH. The coherent electronic wave packet is then probed by angularly resolved photoionization to the cation by an APT generated from a replica of the pump IR pulse at several time delays. Realistic parameters for the pump and the APT are used. Several NeNePo schemes are simulated using different IR carrier frequencies, showing that the delay between the successive attosecond pulses in the train can be used as a filter to probe the different pairs of states present in the coherent electronic wave packet produced by the pump pulse. The dynamical simulations include the pump and the probe pulses to all orders by solving the time-dependent Schrodinger equation using a coupled equation scheme for the manifolds of the anion, neutral, and cation subspaces. We show that an incomplete molecular orientation of the molecule in the laboratory frame does not prevent probing the electronic density localization by angularly resolved photoelectron maps.}, issn = {1089-5639}, doi = {10.1021/jp504592f}, author = {Mignolet, B. and LEVINE, RD and Remacle, F.} } @article { ISI:000340695800004, title = {A full-adder based on reconfigurable DNA-hairpin inputs and DNAzyme computing modules}, journal = {CHEMICAL SCIENCE}, volume = {5}, year = {2014}, month = {SEP}, pages = {3381-3387}, abstract = {In nature, post-transcriptional alternative splicing processes expand the proteome biodiversity providing means to synthesize various protein isoforms. We describe the input-guided assembly of a DNAzyme-based full-adder computing system, which mimics functions of the natural processes by increasing the diversity of logic elements by the reconfiguration of the inputs. The full-adder comprises the simultaneous operation of three inputs that yield two different output signals, acting as sum and carry bits. The DNAzyme-based full-adder system consists of a library of Mg2+-dependent DNAzyme subunits and their substrates that are modified by two different fluorophore/quencher pairs that encode the sum and carry outputs. The input-guided assembly of DNAzyme subunits, formed by three inputs composed of nucleic acid hairpin structures, leads to computing modules that yield the sum and carry outputs of the full-adder. In the presence of a single input the DNAzyme computing module yields the sum fluorescence output. In the presence of two of the inputs, the reconfiguration of the input structures proceeds, leading to an input-guided computing module that yields the carry fluorescence output. By introducing all the three inputs the sequential inter-input hybridization leads to the reconfiguration of the inputs into polymer wires. These include binding sites for two types of DNAzyme and their substrates leading to the carry and sum fluorescence outputs. The advantages of the simultaneous three-input operation of the full-adder and the possibilities to implement DNAzyme-based computing modules for cascading full-adders are discussed.}, issn = {2041-6520}, doi = {10.1039/c4sc00914b}, author = {Orbach, Ron and Wang, Fuan and Lioubashevski, Oleg and LEVINE, RD and Remacle, Francoise and Willner, Itamar} } @article { ISI:000342922000033, title = {Massive isotopic effect in vacuum UV photodissociation of N-2 and implications for meteorite data}, journal = {PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA}, volume = {111}, year = {2014}, month = {OCT 14}, pages = {14704-14709}, abstract = {Nitrogen isotopic distributions in the solar system extend across an enormous range, from -400 parts per thousand, in the solar wind and Jovian atmosphere, to about 5,000 parts per thousand in organic matter in carbonaceous chondrites. Distributions such as these require complex processing of nitrogen reservoirs and extraordinary isotope effects. While theoretical models invoke ion-neutral exchange reactions outside the protoplanetary disk and photochemical self-shielding on the disk surface to explain the variations, there are no experiments to substantiate these models. Experimental results of N-2 photolysis at vacuum UV wavelengths in the presence of hydrogen are presented here, which show a wide range of enriched delta N-15 values from 648 parts per thousand to 13,412 parts per thousand in product NH3, depending upon photodissociation wavelength. The measured enrichment range in photodissociation of N-2, plausibly explains the range of delta N-15 in extraterrestrial materials. This study suggests the importance of photochemical processing of the nitrogen reservoirs within the solar nebula.}, issn = {0027-8424}, doi = {10.1073/pnas.1410440111}, author = {Chakraborty, Subrata and Muskatel, B. H. and Jackson, Teresa L. and Ahmed, Musahid and LEVINE, RD and Thiemens, Mark H.} } @article { ISI:000347720000016, title = {Prediction of molecular response to the measured disturbances on single cells}, journal = {M S-MEDECINE SCIENCES}, volume = {30}, year = {2014}, month = {DEC}, pages = {1129-1135}, issn = {0767-0974}, doi = {10.1051/medsci/20143012016}, author = {Remacle, Francoise and Levine, Raphael D.} } @article { ISI:000341625600061, title = {Surprisal analysis characterizes the free energy time course of cancer cells undergoing epithelial-to-mesenchymal transition}, journal = {PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA}, volume = {111}, year = {2014}, month = {SEP 9}, pages = {13235-13240}, abstract = {The epithelial-to-mesenchymal transition (EMT) initiates the invasive and metastatic behavior of many epithelial cancers. Mechanisms underlying EMT are not fully known. Surprisal analysis of mRNA time course data from lung and pancreatic cancer cells stimulated to undergo TGF-beta 1-induced EMT identifies two phenotypes. Examination of the time course for these phenotypes reveals that EMT reprogramming is a multistep process characterized by initiation, maturation, and stabilization stages that correlate with changes in cell metabolism. Surprisal analysis characterizes the free energy time course of the expression levels throughout the transition in terms of two state variables. The landscape of the free energy changes during the EMT for the lung cancer cells shows a stable intermediate state. Existing data suggest this is the previously proposed maturation stage. Using a single-cell ATP assay, we demonstrate that the TGF-beta 1-induced EMT for lung cancer cells, particularly during the maturation stage, coincides with a metabolic shift resulting in increased cytosolic ATP levels. Surprisal analysis also characterizes the absolute expression levels of the mRNAs and thereby examines the homeostasis of the transcription system during EMT.}, issn = {0027-8424}, doi = {10.1073/pnas.1414714111}, author = {Zadran, Sohila and Arumugam, Rameshkumar and Herschman, Harvey and Phelps, Michael E. and LEVINE, RD} } @article { ISI:000315844500014, title = {Free Energy Rhythms in Saccharomyces cerevisiae: A Dynamic Perspective with Implications for Ribosomal Biogenesis}, journal = {BIOCHEMISTRY}, volume = {52}, year = {2013}, month = {MAR 5}, pages = {1641-1648}, abstract = {To describe the time course of cellular systems, we integrate ideas from thermodynamics and information theory to discuss the work needed to change the state of the cell. The biological example analyzed is experimental microarray transcription level oscillations of yeast in the different phases as characterized by oxygen consumption. Surprisal analysis was applied to identify groups of transcripts that oscillate in concert and thereby to compute changes in free energy with time. Three dominant transcript groups were identified by surprisal analysis. The groups correspond to the respiratory, early, and late reductive phases. Genes involved in ribosome biogenesis peaked at the respiratory phase. The work to prepare the state is shown to be the sum of the contributions of these groups. We paid particular attention to work requirements during ribosomal building, and the correlation with ATP levels and dissolved oxygen. The suggestion that cells in the respiratory phase likely build ribosomes, an energy intensive process, in preparation for protein production during the S phase of the cell cycle is validated by an experiment. Surprisal analysis thereby provided a useful tool for determining the synchronization of transcription events and energetics in a cell in real time.}, issn = {0006-2960}, doi = {10.1021/bi3016982}, author = {Gross, A. and Li, Caroline M. and Remacle, F. and LEVINE, RD} } @article { ISI:000317948000005, title = {Hypoxia induces a phase transition within a kinase signaling network in cancer cells}, journal = {PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA}, volume = {110}, year = {2013}, month = {APR 9}, pages = {E1352-E1360}, abstract = {Hypoxia is a near-universal feature of cancer, promoting glycolysis, cellular proliferation, and angiogenesis. The molecular mechanisms of hypoxic signaling have been intensively studied, but the impact of changes in oxygen partial pressure (pO(2)) on the state of signaling networks is less clear. In a glioblastoma multiforme (GBM) cancer cell model, we examined the response of signaling networks to targeted pathway inhibition between 21\% and 1\% pO(2). We used a microchip technology that facilitates quantification of a panel of functional proteins from statistical numbers of single cells. We find that near 1.5\% pO(2), the signaling network associated with mammalian target of rapamycin (mTOR) complex 1 (mTORC1)-a critical component of hypoxic signaling and a compelling cancer drug target-is deregulated in a manner such that it will be unresponsive to mTOR kinase inhibitors near 1.5\% pO(2), but will respond at higher or lower pO(2) values. These predictions were validated through experiments on bulk GBM cell line cultures and on neurosphere cultures of a human-origin GBM xenograft tumor. We attempt to understand this behavior through the use of a quantitative version of Le Chatelier{\textquoteright}s principle, as well as through a steady-state kinetic model of protein interactions, both of which indicate that hypoxia can influence mTORC1 signaling as a switch. The Le Chatelier approach also indicates that this switch may be thought of as a type of phase transition. Our analysis indicates that certain biologically complex cell behaviors may be understood using fundamental, thermodynamics-motivated principles.}, issn = {0027-8424}, doi = {10.1073/pnas.1303060110}, author = {Wei, Wei and Shi, Qihui and Remacle, Francoise and Qin, Lidong and Shackelford, David B. and Shin, Young Shik and Mischel, Paul S. and LEVINE, RD and Heath, James R.} } @article { ISI:000327100600096, title = {miRNA and mRNA cancer signatures determined by analysis of expression levels in large cohorts of patients}, journal = {PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA}, volume = {110}, year = {2013}, month = {NOV 19}, pages = {19160-19165}, abstract = {Toward identifying a cancer-specific gene signature we applied surprisal analysis to the RNAs expression behavior for a large cohort of breast, lung, ovarian, and prostate carcinoma patients. We characterize the cancer phenotypic state as a shared response of a set of mRNA or microRNAs (miRNAs) in cancer patients versus noncancer controls. The resulting signature is robust with respect to individual patient variability and distinguishes with high fidelity between cancer and noncancer patients. The mRNAs and miRNAs that are implicated in the signature are correlated and are known to contribute to the regulation of cancer-signaling pathways. The miRNA and mRNA networks are common to the noncancer and cancer patients, but the disease modulates the strength of the connectivities. Furthermore, we experimentally assessed the cancer-specific signatures as possible therapeutic targets. Specifically we restructured a single dominant connectivity in the cancer-specific gene network in vitro. We find a deflection from the cancer phenotype, significantly reducing cancer cell proliferation and altering cancer cellular physiology. Our approach is grounded in thermodynamics augmented by information theory. The thermodynamic reasoning is demonstrated to ensure that the derived signature is bias-free and shows that the most significant redistribution of free energy occurs in programming a system between the noncancer and cancer states. This paper introduces a platform that can elucidate miRNA and mRNA behavior on a systems level and provides a comprehensive systematic view of both the energetics of the expression levels of RNAs and of their changes during tumorigenicity.}, issn = {0027-8424}, doi = {10.1073/pnas.1316991110}, author = {Zadran, Sohila and Remacle, F. and LEVINE, RD} } @article { ISI:000325943300018, title = {Molecular decision trees realized by ultrafast electronic spectroscopy}, journal = {PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA}, volume = {110}, year = {2013}, month = {OCT 22}, pages = {17183-17188}, abstract = {The outcome of a light-matter interaction depends on both the state of matter and the state of light. It is thus a natural setting for implementing bilinear classical logic. A description of the state of a time-varying system requires measuring an (ideally complete) set of time-dependent observables. Typically, this is prohibitive, but in weak-field spectroscopy we can move toward this goal because only a finite number of levels are accessible. Recent progress in nonlinear spectroscopies means that nontrivial measurements can be implemented and thereby give rise to interesting logic schemes where the outputs are functions of the observables. Lie algebra offers a natural tool for generating the outcome of the bilinear light-matter interaction. We show how to synthesize these ideas by explicitly discussing three-photon spectroscopy of a bichromophoric molecule for which there are four accessible states. Switching logic would use the on-off occupancies of these four states as outcomes. Here, we explore the use of all 16 observables that define the time-evolving state of the bichromophoric system. The bilinear laser-system interaction with the three pulses of the setup of a 2D photon echo spectroscopy experiment can be used to generate a rich parallel logic that corresponds to the implementation of a molecular decision tree. Our simulations allow relaxation by weak coupling to the environment, which adds to the complexity of the logic operations.}, issn = {0027-8424}, doi = {10.1073/pnas.1314978110}, author = {Fresch, Barbara and Hiluf, Dawit and Collini, Elisabetta and LEVINE, RD and Remacle, F.} } @article { ISI:000314023100005, title = {Perspectives in Metabolic Engineering: Understanding Cellular Regulation Towards the Control of Metabolic Routes}, journal = {APPLIED BIOCHEMISTRY AND BIOTECHNOLOGY}, volume = {169}, year = {2013}, month = {JAN}, pages = {55-65}, abstract = {Metabolic engineering seeks to redirect metabolic pathways through the modification of specific biochemical reactions or the introduction of new ones with the use of recombinant technology. Many of the chemicals synthesized via introduction of product-specific enzymes or the reconstruction of entire metabolic pathways into engineered hosts that can sustain production and can synthesize high yields of the desired product as yields of natural product-derived compounds are frequently low, and chemical processes can be both energy and material expensive; current endeavors have focused on using biologically derived processes as alternatives to chemical synthesis. Such economically favorable manufacturing processes pursue goals related to sustainable development and {\textquoteleft}{\textquoteleft}green chemistry{\textquoteright}{\textquoteright}. Metabolic engineering is a multidisciplinary approach, involving chemical engineering, molecular biology, biochemistry, and analytical chemistry. Recent advances in molecular biology, genome-scale models, theoretical understanding, and kinetic modeling has increased interest in using metabolic engineering to redirect metabolic fluxes for industrial and therapeutic purposes. The use of metabolic engineering has increased the productivity of industrially pertinent small molecules, alcohol-based biofuels, and biodiesel. Here, we highlight developments in the practical and theoretical strategies and technologies available for the metabolic engineering of simple systems and address current limitations.}, issn = {0273-2289}, doi = {10.1007/s12010-012-9951-x}, author = {Zadran, Sohila and Levine, Raphael D.} } @article { ISI:000326366900038, title = {Pump and Probe of Ultrafast Charge Reorganization in Small Peptides: A Computational Study through Sudden Ionizations}, journal = {JOURNAL OF PHYSICAL CHEMISTRY A}, volume = {117}, year = {2013}, month = {OCT 10}, pages = {10513-10525}, abstract = {The ultrafast migratory dynamics of the nonstationary hole resulting from a sudden ionization of the small tetrapeptides, Trp-(Leu)(3) and Tyr-(Ala)(3), is studied using as input a high level quantum chemistry description of the electronic structure for extended conformers computed for frozen nuclei. The sudden ionization process prepares a localized electronic wavepacket that is a superposition of a few stationary states of the cation that are energetically allowed. The superposition evolves field-free until a second ionization to the dication. The wavelength and polarization of the first ultrashort VUV ionizing pulse can be used to tailor the amplitudes on the states of the cation and the initial localization of the hole. For these molecular chains that extend over 15 angstrom, the most efficient mechanism for charge migration is sequential, involving coherent transitions between neighbor and next neighbor amino-acid subunits. The migration of the hole is probed by a second sudden ionization leading to a dication peptide. Its time scale is in the range of a few to a dozen of femtoseconds depending on the initial state of the cation built by the ionization process. The computed angular distributions provide a clear signature of the field-free dynamics between the two sudden ionization processes. Our results are consistent with the experimental observation that the charge transfer is activated, meaning that an excess energy above the ionization potential of the cation is required for facile migration of charge.}, issn = {1089-5639}, doi = {10.1021/jp407295t}, author = {Kus, T. and Mignolet, B. and LEVINE, RD and Remacle, F.} } @article { ISI:000318008400063, title = {Surprisal Analysis of Transcripts Expression Levels in the Presence of Noise: A Reliable Determination of the Onset of a Tumor Phenotype}, journal = {PLOS ONE}, volume = {8}, year = {2013}, month = {APR 23}, abstract = {Towards a reliable identification of the onset in time of a cancer phenotype, changes in transcription levels in cell models were tested. Surprisal analysis, an information-theoretic approach grounded in thermodynamics, was used to characterize the expression level of mRNAs as time changed. Surprisal Analysis provides a very compact representation for the measured expression levels of many thousands of mRNAs in terms of very few - three, four - transcription patterns. The patterns, that are a collection of transcripts that respond together, can be assigned definite biological phenotypic role. We identify a transcription pattern that is a clear marker of eventual malignancy. The weight of each transcription pattern is determined by surprisal analysis. The weight of this pattern changes with time; it is never strictly zero but it is very low at early times and then rises rather suddenly. We suggest that the low weights at early time points are primarily due to experimental noise. We develop the necessary formalism to determine at what point in time the value of that pattern becomes reliable. Beyond the point in time when a pattern is deemed reliable the data shows that the pattern remain reliable. We suggest that this allows a determination of the presence of a cancer forewarning. We apply the same formalism to the weight of the transcription patterns that account for healthy cell pathways, such as apoptosis, that need to be switched off in cancer cells. We show that their weight eventually falls below the threshold. Lastly we discuss patient heterogeneity as an additional source of fluctuation and show how to incorporate it within the developed formalism.}, issn = {1932-6203}, doi = {10.1371/journal.pone.0061554}, author = {Gross, Ayelet and Levine, Raphael D.} } @article { ISI:000301712600070, title = {On a fundamental structure of gene networks in living cells}, journal = {PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA}, volume = {109}, year = {2012}, month = {MAR 20}, pages = {4702-4707}, abstract = {Computers are organized into hardware and software. Using a theoretical approach to identify patterns in gene expression in a variety of species, organs, and cell types, we found that biological systems similarly are comprised of a relatively unchanging hardware-like gene pattern. Orthogonal patterns of software-like transcripts vary greatly, even among tumors of the same type from different individuals. Two distinguishable classes could be identified within the hardware-like component: those transcripts that are highly expressed and stable and an adaptable subset with lower expression that respond to external stimuli. Importantly, we demonstrate that this structure is conserved across organisms. Deletions of transcripts from the highly stable core are predicted to result in cell mortality. The approach provides a conceptual thermodynamic-like framework for the analysis of gene-expression levels and networks and their variations in diseased cells.}, issn = {0027-8424}, doi = {10.1073/pnas.1200790109}, author = {Kravchenko-Balasha, Nataly and Levitzki, Alexander and Goldstein, Andrew and Rotter, Varda and Gross, A. and Remacle, F. and LEVINE, RD} } @article { ISI:000311714300015, title = {Localized electron dynamics in attosecond-pulse-excited molecular systems: Probing the time-dependent electron density by sudden photoionization}, journal = {PHYSICAL REVIEW A}, volume = {86}, year = {2012}, month = {NOV 30}, abstract = {Ultrafast UV excitation can prepare a nonstationary coherent superposition of molecular electronic states. The purely electronic dynamics before the onset of nuclear motion can be probed by a sudden XUV ionization of the electronic wave packet. Dynamical computations at the many-electron level on the LiH and 1-azabicyclo[3.3.3]undecane (C10H19N) molecules show that molecular frame photoelectron angular distributions reflect the spatial localization and undulations of the electronic coherent superposition accessed by the initial ultrafast UV excitation. The sudden ionization is sensitive to interference effects.}, issn = {1050-2947}, doi = {10.1103/PhysRevA.86.053429}, author = {Mignolet, B. and LEVINE, RD and Remacle, F.} } @article { ISI:000313627700028, title = {Logic reversibility and thermodynamic irreversibility demonstrated by DNAzyme-based Toffoli and Fredkin logic gates}, journal = {PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA}, volume = {109}, year = {2012}, month = {DEC 26}, pages = {21228-21233}, abstract = {The Toffoli and Fredkin gates were suggested as a means to exhibit logic reversibility and thereby reduce energy dissipation associated with logic operations in dense computing circuits. We present a construction of the logically reversible Toffoli and Fredkin gates by implementing a library of predesigned Mg2+-dependent DNAzymes and their respective substrates. Although the logical reversibility, for which each set of inputs uniquely correlates to a set of outputs, is demonstrated, the systems manifest thermodynamic irreversibility originating from two quite distinct and nonrelated phenomena. (i) The physical readout of the gates is by fluorescence that depletes the population of the final state of the machine. This irreversible, heat-releasing process is needed for the generation of the output. (ii) The DNAzyme-powered logic gates are made to operate at a finite rate by invoking downhill energy-releasing processes. Even though the three bits of Toffoli{\textquoteright}s and Fredkin{\textquoteright}s logically reversible gates manifest thermodynamic irreversibility, we suggest that these gates could have important practical implication in future nanomedicine.}, issn = {0027-8424}, doi = {10.1073/pnas.1219672110}, author = {Orbach, Ron and Remacle, Franoise and LEVINE, RD and Willner, Itamar} } @article { ISI:000307645400011, title = {Maximal entropy multivariate analysis}, journal = {MOLECULAR PHYSICS}, volume = {110}, year = {2012}, pages = {1659-1668}, abstract = {A methodology is developed for the analysis of multivariate data by maximal entropy and it is shown how the surprisal reduces to the more familiar bivariate and univariate forms. When multivariate data is available it is shown how the uni- or bi-variate surprisal parameters can be expressed as a sum of terms containing contributions of different pathways. But if averaging so as to reduce the number of variables is performed before the data analysis then all that one can determine is the sum but not the individual contributions: averaging completely hides essential details and correlations. The formalism is illustrated by an application to ultrafast translational equilibration that occurs when a cold rare gas cluster impacts a hard surface at a hypersonic speed.}, issn = {0026-8976}, doi = {10.1080/00268976.2012.665192}, author = {Remacle, F. and Arumugam, Rameshkumar and LEVINE, RD} } @article { ISI:000312177000005, title = {Multi Project: Multi-Valued and Parallel Molecular Logic}, journal = {INTERNATIONAL JOURNAL OF UNCONVENTIONAL COMPUTING}, volume = {8}, year = {2012}, pages = {307-312}, issn = {1548-7199}, author = {Collini, E. and LEVINE, RD and Remacle, F. and Rogge, S. and WILLNER, I} } @article { ISI:000312122100011, title = {Quantitating Cell-Cell Interaction Functions with Applications to Glioblastoma Multiforme Cancer Cells}, journal = {NANO LETTERS}, volume = {12}, year = {2012}, month = {DEC}, pages = {6101-6106}, abstract = {We report on a method for quantitating the distance dependence of cell-cell interactions. We employ a microchip design that permits a multiplex, quantitative protein assay from statistical numbers of cell pairs, as a function of cell separation, with a 0.15 nL volume microchamber. We interrogate interactions between pairs of model brain cancer cells by assaying for six functional proteins associated with PI3k signaling. At short incubation times, cells do not appear to influence each other, regardless of cell separation. For 6 h incubation times, the cells exert an inhibiting influence on each other at short separations and a predominately activating influence at large separation. Protein-specific cell-cell interaction functions are extracted, and by assuming pairwise additivity of those interactions, the functions are shown to correctly predict the results from three-cell experiments carried out under the identical conditions.}, issn = {1530-6984}, doi = {10.1021/nl302748q}, author = {Wang, Jun and Tham, Douglas and Wei, Wei and Shin, Young Shik and Ma, Chao and Ahmad, Habib and Shi, Qihui and Yu, Jenkan and Levine, Raphael D. and Heath, James R.} } @article { ISI:000311460400029, title = {Ultrafast Predissociation Mechanism of the (1)Pi(u) States of N-14(2) and Its Isotopomers upon Attosecond Excitation from the Ground State}, journal = {JOURNAL OF PHYSICAL CHEMISTRY A}, volume = {116}, year = {2012}, month = {NOV 22}, pages = {11311-11318}, abstract = {The computed time evolution of excited electronic and nuclear:states:. of dinitrogen following a broad laser pulse excitation of the dipole allowed singlet Pi states is discussed. The computations use two complementary methods to solve the time-dependent Schrodinger equation of the molecule. The electronic evolution is described as spanning seven states, the three dipole-allowed singlet states (b,c,o(1)Pi(u)) and four triplet states (C,C{\textquoteright},F,G(3)Pi(u)). Spin orbit coupling mixes states of the two manifolds. The computed dynamics includes the attosecond pulse single photon pumping from the electronic ground state. The ultrafast exit to the continuum from the bound states that are optically excited and the large isotope effect on this process are used as a probe of the electron dynamics as coupled to the Onset of the nuclear motion. For -{\textquoteright}4N2-, prompt predissociation to the continuum of the repulsive C{\textquoteright}(3)Pi(u) state is facilitated primarily by the b(1)Pi(u)(v=3)-C-3 Pi(u)(v = 9) coupling whereas for N-15(2) it is the b1 Pi(u) (v =4)-C-3 Pi(u)(v =10) coupling term. Predissociation from the F3 Pi u and G(3)Pi(u) stateS is important at the high energies because of their strong coupling to the continuum.}, issn = {1089-5639}, doi = {10.1021/jp305354h}, author = {Muskatel, B. H. and Remacle, F. and LEVINE, RD} } @article { ISI:000286743100004, title = {Attosecond pumping of nonstationary electronic states of LiH: Charge shake-up and electron density distortion}, journal = {PHYSICAL REVIEW A}, volume = {83}, year = {2011}, month = {JAN 27}, abstract = {Electronic reorganization during and after excitation by an intense ultrashort pulse is computed for LiH in a many-electron multireference time-dependent approach at a fixed nuclear geometry. The electronic dipole moment is used to probe the temporal response of the charge density. Above a field-strength threshold, there is an extensive Stark shifting and Rabi broadening of levels with corresponding distortion of the charge distribution whose response at strong fields is neither adiabatic nor diabatic. A nonresonant IR pulse is more effective in inducing charge shake-up during the pulse.}, issn = {1050-2947}, doi = {10.1103/PhysRevA.83.013411}, author = {Remacle, F. and LEVINE, RD} } @article { ISI:000291876500001, title = {Convergence of Logic of Cellular Regulation in Different Premalignant Cells by an Information Theoretic Approach}, journal = {BMC SYSTEMS BIOLOGY}, volume = {5}, year = {2011}, month = {MAR 16}, abstract = {Background: Surprisal analysis is a thermodynamic-like molecular level approach that identifies biological constraints that prevents the entropy from reaching its maximum. To examine the significance of altered gene expression levels in tumorigenesis we apply surprisal analysis to the WI-38 model through its precancerous states. The constraints identified by the analysis are transcription patterns underlying the process of transformation. Each pattern highlights the role of a group of genes that act coherently to define a transformed phenotype. Results: We identify a major transcription pattern that represents a contraction of signaling networks accompanied by induction of cellular proliferation and protein metabolism, which is essential for full transformation. In addition, a more minor, {\textquoteleft}{\textquoteleft}tumor signature{\textquoteright}{\textquoteright} transcription pattern completes the transformation process. The variation with time of the importance of each transcription pattern is determined. Midway through the transformation, at the stage when cells switch from slow to fast growth rate, the major transcription pattern undergoes a total inversion of its weight while the more minor pattern does not contribute before that stage. Conclusions: A similar network reorganization occurs in two very different cellular transformation models: WI-38 and the cervical cancer HF1 models. Our results suggest that despite differences in a list of transcripts expressed in different cancer models the rationale of the network reorganization remains essentially the same.}, issn = {1752-0509}, doi = {10.1186/1752-0509-5-42}, author = {Kravchenko-Balasha, Nataly and Remacle, F. and Gross, Ayelet and Rotter, Varda and Levitzki, Alexander and LEVINE, RD} } @article { ISI:000288003900015, title = {DNA computing circuits using libraries of DNAzyme subunits (vol 5, pg 417, 2010)}, journal = {NATURE NANOTECHNOLOGY}, volume = {6}, year = {2011}, month = {MAR}, pages = {190}, issn = {1748-3387}, doi = {10.1038/NNANO.2011.23}, author = {Elbaz, Johann and Lioubashevski, Oleg and Wang, Fuan and Remacle, Francoise and Levine, Raphael D. and Willner, Itamar} } @article { ISI:000288895700004, title = {Logic operations in a doped solid driven by stimulated Raman adiabatic passage}, journal = {PHYSICAL REVIEW A}, volume = {83}, year = {2011}, month = {MAR 29}, abstract = {We experimentally demonstrate classical-optical logic operations in a solid-state memory, coherently driven by variants of stimulated Raman adiabatic passage (STIRAP). Cyclic transfer of atomic populations permits the implementation of a flip-flop or XOR gate, with up to eight optical input operations. Observation of stimulated emission as an additional output channel enables the setup of a STIRAP-driven full adder for three optical input bits (or two input bits and a memory bit).}, issn = {1050-2947}, doi = {10.1103/PhysRevA.83.033421}, author = {Beil, F. and Halfmann, T. and Remacle, F. and LEVINE, RD} } @article { ISI:000290830900008, title = {Protein Signaling Networks from Single Cell Fluctuations and Information Theory Profiling}, journal = {BIOPHYSICAL JOURNAL}, volume = {100}, year = {2011}, month = {MAY 18}, pages = {2378-2386}, abstract = {Protein signaling networks among cells play critical roles in a host of pathophysiological processes, from inflammation to tumorigenesis. We report on an approach that integrates microfluidic cell handling, in situ protein secretion profiling, and information theory to determine an extracellular protein-signaling network and the role of perturbations. We assayed 12 proteins secreted from human macrophages that were subjected to lipopolysaccharide challenge, which emulates the macrophage-based innate immune responses against Gram-negative bacteria. We characterize the fluctuations in protein secretion of single cells, and of small cell colonies (n = 2, 3, ... ), as a function of colony size. Measuring the fluctuations permits a validation of the conditions required for the application of a quantitative version of the Le Chatelier{\textquoteright}s principle, as derived using information theory. This principle provides a quantitative prediction of the role of perturbations and allows a characterization of a protein-protein interaction network.}, issn = {0006-3495}, doi = {10.1016/j.bpj.2011.04.025}, author = {Shin, Young Shik and Remacle, F. and Fan, Rong and Hwang, Kiwook and Wei, Wei and Ahmad, Habib and LEVINE, RD and Heath, James R.} } @article { ISI:000289954300029, title = {Stereocontrol of attosecond time-scale electron dynamics in ABCU using ultrafast laser pulses: a computational study}, journal = {PHYSICAL CHEMISTRY CHEMICAL PHYSICS}, volume = {13}, year = {2011}, pages = {8331-8344}, abstract = {The attosecond time-scale electronic dynamics induced by an ultrashort laser pulse is computed using a multi configuration time dependent approach in ABCU (C(10)H(19)N), a medium size polyatomic molecule with a rigid cage geometry. The coupling between the electronic states induced by the strong pulse is included in the many electron Hamiltonian used to compute the electron dynamics. We show that it is possible to implement control of the electron density stereodynamics in this medium size molecule by varying the characteristics of the laser pulse, for example by polarizing the electric field either along the N-C axis of the cage, or in the plane perpendicular to it. The excitation produces an oscillatory, non-stationary, electronic state that exhibits localization of the electron density in different parts of the molecule both during and after the pulse. The coherent oscillations of the non-stationary electronic state are also demonstrated through the alternation of the dipole moment of the molecule.}, issn = {1463-9076}, doi = {10.1039/c1cp20094a}, author = {Mignolet, B. and Gijsbertsen, A. and Vrakking, M. J. J. and LEVINE, RD and Remacle, F.} } @article { ISI:000289413600025, title = {On the strong and selective isotope effect in the UV excitation of N-2 with implications toward the nebula and Martian atmosphere}, journal = {PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA}, volume = {108}, year = {2011}, month = {APR 12}, pages = {6020-6025}, abstract = {Isotopic effects associated with molecular absorption are discussed with reference to natural phenomena including early solar system processes, Titan and terrestrial atmospheric chemistry, and Martian atmospheric evolution. Quantification of the physicochemical aspects of the excitation and dissociation processes may lead to enhanced understanding of these environments. Here we examine a physical basis for an additional isotope effect during photolysis of molecular nitrogen due to the coupling of valence and Rydberg excited states. The origin of this isotope effect is shown to be the coupling of diabatic electronic states of different bonding nature that occurs after the excitation of these states. This coupling is characteristic of energy regimes where two or more excited states are nearly crossing or osculating. A signature of the resultant isotope effect is a window of rapid variation in the otherwise smooth distribution of oscillator strengths vs. frequency. The reference for the discussion is the numerical solution of the time dependent Schrodinger equation for both the electronic and nuclear modes with the light field included as part of the Hamiltonian. Pumping is to all extreme UV dipole-allowed, valence and Rydberg, excited states of N-2. The computed absorption spectra are convoluted with the solar spectrum to demonstrate the importance of including this isotope effect in planetary, interstellar molecular cloud, and nebular photochemical models. It is suggested that accidental resonance with strong discrete lines in the solar spectrum such as the CIII line at 97.703 nm can also have a marked effect.}, issn = {0027-8424}, doi = {10.1073/pnas.1102767108}, author = {Muskatel, B. H. and Remacle, F. and Thiemens, Mark H. and LEVINE, RD} } @article { ISI:000294163500027, title = {Integrated logic circuits using single-atom transistors}, journal = {PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA}, volume = {108}, year = {2011}, month = {AUG 23}, pages = {13969-13972}, abstract = {Scaling down the size of computing circuits is about to reach the limitations imposed by the discrete atomic structure of matter. Reducing the power requirements and thereby dissipation of integrated circuits is also essential. New paradigms are needed to sustain the rate of progress that society has become used to. Single-atom transistors, SATs, cascaded in a circuit are proposed as a promising route that is compatible with existing technology. We demonstrate the use of quantum degrees of freedom to perform logic operations in a complementary-metal-oxide-semiconductor device. Each SAT performs multilevel logic by electrically addressing the electronic states of a dopant atom. A single electron transistor decodes the physical multivalued output into the conventional binary output. A robust scalable circuit of two concatenated full adders is reported, where by utilizing charge and quantum degrees of freedom, the functionality of the transistor is pushed far beyond that of a simple switch.}, issn = {0027-8424}, doi = {10.1073/pnas.1109935108}, author = {Mol, J. A. and Verduijn, J. and LEVINE, RD and Remacle, F. and Rogge, S.} } @article { ISI:000293301000012, title = {Whose Entropy: A Maximal Entropy Analysis of Phosphorylation Signaling}, journal = {JOURNAL OF STATISTICAL PHYSICS}, volume = {144}, year = {2011}, month = {JUL}, pages = {429-442}, abstract = {High throughput experiments, characteristic of studies in systems biology, produce large output data sets often at different time points or under a variety of related conditions or for different patients. In several recent papers the data is modeled by using a distribution of maximal information-theoretic entropy. We pose the question: {\textquoteleft}whose entropy{\textquoteright} meaning how do we select the variables whose distribution should be compared to that of maximal entropy. The point is that different choices can lead to different answers. Due to the technological advances that allow for the system-wide measurement of hundreds to thousands of events from biological samples, addressing this question is now part of the analysis of systems biology datasets. The analysis of the extent of phosphorylation in reference to the transformation potency of Bcr-Abl fusion oncogene mutants is used as a biological example. The approach taken seeks to use entropy not simply as a statistical measure of dispersion but as a physical, thermodynamic, state function. This highlights the dilemma of what are the variables that describe the state of the signaling network. Is what matters Boolean, spin-like, variables that specify whether a particular phosphorylation site is or is not actually phosphorylated. Or does the actual extent of phosphorylation matter. Last but not least is the possibility that in a signaling network some few specific phosphorylation sites are the key to the signal transduction even though these sites are not at any time abundantly phosphorylated in an absolute sense.}, issn = {0022-4715}, doi = {10.1007/s10955-011-0215-x}, author = {Remacle, F. and Graeber, T. G. and LEVINE, RD} } @article { ISI:000279106500014, title = {DNA computing circuits using libraries of DNAzyme subunits}, journal = {NATURE NANOTECHNOLOGY}, volume = {5}, year = {2010}, month = {JUN}, pages = {417-422}, abstract = {Biological systems that are capable of performing computational operations(1-3) could be of use in bioengineering and nanomedicine(4,5), and DNA and other biomolecules have already been used as active components in biocomputational circuits(6-13). There have also been demonstrations of DNA/RNA-enzyme-based automatons(12), logic control of gene expression(14), and RNA systems for processing of intracellular information(15,16). However, for biocomputational circuits to be useful for applications it will be necessary to develop a library of computing elements, to demonstrate the modular coupling of these elements, and to demonstrate that this approach is scalable. Here, we report the construction of a DNA-based computational platform that uses a library of catalytic nucleic acids (DNAzymes)(10), and their substrates, for the input-guided dynamic assembly of a universal set of logic gates and a half-adder/half-subtractor system. We demonstrate multilayered gate cascades, fan-out gates and parallel logic gate operations. In response to input markers, the system can regulate the controlled expression of anti-sense molecules, or aptamers, that act as inhibitors for enzymes.}, issn = {1748-3387}, doi = {10.1038/NNANO.2010.88}, author = {Elbaz, Johann and Lioubashevski, Oleg and Wang, Fuan and Remacle, Francoise and Levine, Raphael D. and Willner, Itamar} } @article { ISI:000278246000074, title = {Information-theoretic analysis of phenotype changes in early stages of carcinogenesis}, journal = {PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA}, volume = {107}, year = {2010}, month = {JUN 1}, pages = {10324-10329}, abstract = {Cancer is a multistep process characterized by altered signal transduction, cell growth, and metabolism. To identify such processes in early carcinogenesis we use an information theoretic approach to characterize gene expression quanti. ed as mRNA levels in primary keratinocytes (K) and human papillomavirus 16 (HPV16)-transformed keratinocytes (HF1 cells) from early (E) and late (L) passages and from benzo(a) pyrene-treated (BP) L cells. Our starting point is that biological signaling processes are subjected to the same quantitative laws as inanimate, nonequilibrium chemical systems. Environmental and genomic constraints thereby limit the maximal thermodynamic entropy that the biological system can reach. The procedure uncovers the changes in gene expression patterns in different networks and de. nes the signi. cance of each altered network in the establishment of a particular phenotype. The development of transformed HF1 cells is shown to be represented by one major transcription pattern that is important at all times. Two minor transcription patterns are also identi. ed, one that contributes at early times and a distinguishably different pattern that contributes at later times. All three transcription patterns de. ned by our analysis were validated by gene expression values and biochemical means. The major transcription pattern includes reduced transcripts participating in the apoptotic network and enhanced transcripts participating in cell cycle, glycolysis, and oxidative phosphorylation. The two minor patterns identify genes that are mainly involved in lipid or carbohydrate metabolism.}, issn = {0027-8424}, doi = {10.1073/pnas.1005283107}, author = {Remacle, F. and Kravchenko-Balasha, Nataly and Levitzki, Alexander and LEVINE, RD} } @article { ISI:000279106500019, title = {Logic implementations using a single nanoparticle-protein hybrid}, journal = {NATURE NANOTECHNOLOGY}, volume = {5}, year = {2010}, month = {JUN}, pages = {451-457}, abstract = {A Set-Reset machine is the simplest logic circuit with a built-in memory. Its output is a (nonlinear) function of the input and of the state stored in the machine{\textquoteright}s memory. Here, we report a nanoscale Set-Reset machine operating at room temperature that is based on a 5-nm silicon nanoparticle attached to the inner pore of a stable circular protein. The nanoparticle-protein hybrid can also function as a balanced ternary multiplier. Conductive atomic force microscopy is used to implement the logic input and output operations, and the processing of the logic Set and Reset operations relies on the finite capacitance of the nanoparticle provided by the good electrical isolation given by the protein, thus enabling stability of the logic device states. We show that the machine can be cycled, such that in every successive cycle, the previous state in the memory is retained as the present state. The energy cost of one cycle of computation is minimized to the cost of charging this state.}, issn = {1748-3387}, doi = {10.1038/NNANO.2010.62}, author = {Medalsy, Izhar and Klein, Michael and Heyman, Arnon and Shoseyov, Oded and Remacle, F. and LEVINE, RD and Danny Porath} } @article { ISI:000276159500075, title = {Maximal entropy inference of oncogenicity from phosphorylation signaling}, journal = {PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA}, volume = {107}, year = {2010}, month = {MAR 30}, pages = {6112-6117}, abstract = {Point mutations in the phosphorylation domain of the Bcr-Abl fusion oncogene give rise to drug resistance in chronic myelogenous leukemia patients. These mutations alter kinase-mediated signaling function and phenotypic outcome. An information theoretic analysis of the correlation of phosphoproteomic profiling and transformation potency of the oncogene in different mutants is presented. The theory seeks to predict the leukemic transformation potency from the observed signaling by constructing a distribution of maximal entropy of site-specific phosphorylation events. The theory is developed with special reference to systems biology where high throughput measurements are typical. We seek sets of phosphorylation events most contributory to predicting the phenotype by determining the constraints on the signaling system. The relevance of a constraint is measured by how much it reduces the value of the entropy from its global maximum, where all events are equally likely. Application to experimental phospho-proteomics data for kinase inhibitor-resistant mutants shows that there is one dominant constraint and that other constraints are not relevant to a similar extent. This single constraint accounts for much of the correlation of phosphorylation events with the oncogenic potency and thereby usefully predicts the trends in the phenotypic output. An additional constraint possibly accounts for biological fine structure.}, issn = {0027-8424}, doi = {10.1073/pnas.1001149107}, author = {Graeber, T. G. and Heath, J. R. and Skaggs, B. J. and Phelps, M. E. and Remacle, F. and LEVINE, RD} } @article { ISI:000274933500006, title = {Redox-Executed Logic Operations through the Reversible Voltammetric Response Characteristics of Electroactive Self-Assembled Monolayers}, journal = {AUSTRALIAN JOURNAL OF CHEMISTRY}, volume = {63}, year = {2010}, pages = {173-183}, abstract = {We propose charge quantization in electrochemical oxidation-reduction (redox) systems as a route to performing logical operations efficiently and reversibly. The theory is based on the interfacial potential distribution for electrodes coated with electroactive self-assembled molecular films. We monitor the change in the oxidation number by studying the current as a function of the working and reference electrode potentials and of the temperature. Diamond-shaped regions can be defined that delineate the stability of a given redox species as a function of the applied and reference potentials. Using these electrochemical Coulomb diamonds, we then show the principles for the design of a complete set of binary gates and a finite-state set-reset machine. We demonstrate the analogies between these redox systems and nanoscale solid-state systems where the charging energy is finite. Redox systems allow simple logic operations at room temperature because typically the standard potential is higher than the thermal energy.}, issn = {0004-9425}, doi = {10.1071/CH09504}, author = {Periyasamy, Ganga and LEVINE, RD and Remacle, F.} } @article { ISI:000274179900067, title = {Ternary logic implemented on a single dopant atom field effect silicon transistor}, journal = {APPLIED PHYSICS LETTERS}, volume = {96}, year = {2010}, month = {JAN 25}, abstract = {We provide an experimental proof of principle for a ternary multiplier realized in terms of the charge state of a single dopant atom embedded in a fin field effect transistor (Fin-FET). Robust reading of the logic output is made possible by using two channels to measure the current flowing through the device and the transconductance. A read out procedure that allows for voltage gain is proposed. Long numbers can be multiplied by addressing a sequence of Fin-FET transistors in a row.}, issn = {0003-6951}, doi = {10.1063/1.3297906}, author = {Klein, M. and Mol, J. A. and Verduijn, J. and Lansbergen, G. P. and Rogge, S. and LEVINE, RD and Remacle, F.} } @article { ISI:000285521800015, title = {All-DNA finite-state automata with finite memory}, journal = {PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA}, volume = {107}, year = {2010}, month = {DEC 21}, pages = {21996-22001}, abstract = {Biomolecular logic devices can be applied for sensing and nanomedicine. We built three DNA tweezers that are activated by the inputs H+/OH-; Hg2+/cysteine; nucleic acid linker/complementary antilinker to yield a 16-states finite-state automaton. The outputs of the automata are the configuration of the respective tweezers (opened or closed) determined by observing fluorescence from a fluorophore/quencher pair at the end of the arms of the tweezers. The system exhibits a memory because each current state and output depend not only on the source configuration but also on past states and inputs.}, issn = {0027-8424}, doi = {10.1073/pnas.1015858107}, author = {Wang, Zhen-Gang and Elbaz, Johann and Remacle, F. and LEVINE, RD and Willner, Itamar} } @article { ISI:000284738900009, title = {Electrically Addressing a Molecule-Like Donor Pair in Silicon: An Atomic Scale Cyclable Full Adder Logic}, journal = {JOURNAL OF PHYSICAL CHEMISTRY C}, volume = {114}, year = {2010}, month = {DEC 9}, pages = {20380-20386}, abstract = {Electrical spectroscopy of a heteroatomic molecule-like shallow-donor pair in silicon can switch the molecule between two ionic states of opposite polarities. We study this charge reorganization theoretically by solving the time-dependent Schroedinger equation on a grid using an effective mass model. The ability to control the charge reorganization by applying external electrical fields is then used to design a cyclable full-adder that operates as a nonlinear finite state machine. The logic operations, equivalent to 32 switches, are implemented by realistic pulse voltages that induce diabatic and adiabatic charge transfer between the wells of the two donors. A RF-SET is used for the read out by charge detection.}, issn = {1932-7447}, doi = {10.1021/jp103524d}, author = {Yan, Yonghong and Mol, J. A. and Verduijn, J. and Rogge, S. and LEVINE, RD and Remacle, F.} } @article { ISI:000263093800003, title = {Electrochemically Driven Sequential Machines: An Implementation of Copper Rotaxanes}, journal = {CHEMISTRY-A EUROPEAN JOURNAL}, volume = {15}, year = {2009}, pages = {1310-1313}, issn = {0947-6539}, doi = {10.1002/chem.200802249}, author = {Periyasamy, Ganga and Collin, Jean-Paul and Sauvage, Jean-Pierre and Levine, Raphael D. and Remacle, Francoise} } @article { ISI:000207857808059, title = {PHYS 191-Ultrafast hole migration modular molecules from small peptides to hydrogen bonded clusters}, journal = {ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY}, volume = {237}, year = {2009}, month = {MAR 22}, issn = {0065-7727}, author = {Remacle, Francoise and Levine, Raphael D.} } @article { ISI:000262870500022, title = {Reconfigurable Logic Devices on a Single Dopant Atom-Operation up to a Full Adder by Using Electrical Spectroscopy}, journal = {CHEMPHYSCHEM}, volume = {10}, year = {2009}, month = {JAN 12}, pages = {162-173}, abstract = {A silicon field-effect transistor is operated as a logic circuit by electrically addressing the ground and excited electronic states of an embedded single dopant atom. Experimental results-complemented by analytical and computational calculations-are presented. First, we show how a complete set of binary logic gates can be realized on the same hardware. Then, we show that these gates can be operated in parallel on the very some dopant up to the logic level of a full adder. To use the device not as a switch but as a full logic circuit, we make essential use of the excited electronic states of the dopant and of the ability to shift their energy by gating. The experimental ability to use two channels to measure the current flowing through the device and the conductance (dI/dV) allows for a robust reading of the output of the logic operations.}, issn = {1439-4235}, doi = {10.1002/cphc.200800568}, author = {Klein, Michael and Lansbergen, Gabriel P. and Mol, Jan A. and Rogge, Sven and Levine, Raphael D. and Remacle, Francoise} } @article { ISI:000272205000017, title = {Electronic wave packet motion in water dimer cation: A many electron description}, journal = {CHEMICAL PHYSICS}, volume = {366}, year = {2009}, month = {DEC 10}, pages = {129-138}, abstract = {The time evolution of a non-stationary electronic wave packet created by a sudden ionization is computed using a multi-reference time-dependent approach at a frozen geometry of the nuclei. The methodology is illustrated for the water dimer cation. The electron density as well as the dipole moment are computed as a function of time and used as a probe for the charge migration following upon the sudden removal of a valence electron. It is shown that there is significant purely electronic dynamics on a few femtosecond time scale and that the characteristics of the charge motion depend of the degree of localization of the initial hole formed in the impulsive ionization process. (C) 2009 Elsevier B.V. All rights reserved.}, issn = {0301-0104}, doi = {10.1016/j.chemphys.2009.08.004}, author = {Periyasamy, Ganga and LEVINE, RD and Remacle, F.} } @article { ISI:000265383200115, title = {The Elimination of Redundant Constraints in Surprisal Analysis of Unimolecular Dissociation and Other Endothermic Processes}, journal = {JOURNAL OF PHYSICAL CHEMISTRY A}, volume = {113}, year = {2009}, month = {APR 23}, pages = {4658-4664}, abstract = {It is well understood that energy rich polyatomic molecules do not dissociate promptly because the number, P, of their energy states far exceeds the number, N, of the decay channels. In the simplest RRK theory, the fraction N/P is the probability of dissociation. We discuss the distribution of the decay rates of maximal entropy and conclude that it is governed by at most N linearly independent constraints, N < P, or, more typically, N , issn = {1089-5639}, doi = {10.1021/jp811463h}, author = {Remacle, F. and LEVINE, RD} } @article { ISI:000270388200017, title = {The post-Born-Oppenheimer regime: dynamics of electronic motion in molecules by attosecond few-cycle spectroscopy}, journal = {PHYSICA SCRIPTA}, volume = {80}, year = {2009}, note = {17th European Conference on Dynamics of Molecular Systems (MOLEC XVII), St Petersburg, RUSSIA, AUG 23-29, 2008}, month = {OCT}, abstract = {Dynamics of electronic motion when the nuclei are clamped is discussed and shown to be always described as a superposition of adiabatic electronic states. These states are stationary when the nuclei are clamped but their superposition leads to multiply periodic motion where the natural frequencies are the differences in the energies of the adiabatic electronic states. When one or more of the frequencies are low and the atoms are allowed to move, the electronic rearrangement is commensurate with the motion of the nuclei. This is the usual breakdown of the Born-Oppenheimer approximation. But when the electronic frequencies are higher there is an electronic motion before the nuclei move. The motion can be demonstrated through expectation values such as the multipole moments of the charge distribution. Such superposition states will be excited when the laser pulse width in energy exceeds the spacings of the states. For low-lying valence excited or low Rydberg states this requires a femtosecond or shorter laser pulse. Since the carrier frequency has to be comparable to the excitation energy, the required laser pulses must span only a few cycles.}, issn = {0031-8949}, doi = {10.1088/0031-8949/80/04/048101}, author = {Muskatel, B. H. and Remacle, F. and LEVINE, RD} } @article { ISI:000253713700015, title = {Pump and probe ultrafast electron dynamics in LiH: a computational study}, journal = {NEW JOURNAL OF PHYSICS}, volume = {10}, year = {2008}, month = {FEB 29}, abstract = {A time-dependent multiconfiguration method with a large electronic basis set is used to compute the response of all the electrons of LiH to a few-cycle intense pump field followed by a probe pulse. The ultrashort pump pulse excites a coherent superposition of stationary electronic states and, by changing the pump parameters such as intensity, duration, polarization and phase of carrier frequency, one can steer the motion of the electrons. Particular attention is given to the control provided by the polarization and by the phase. For example, a change in polarization is used to select an electronic wave packet that is rotating in a plane perpendicular to the bond or rotation in a plane containing the bond. The electronic wave packet can be probed by a delayed second pulse. This delayed probe pulse is also included in the Hamiltonian with the result that the frequency dispersed probe spectrum can be computed and displayed as a two-dimensional plot.}, issn = {1367-2630}, doi = {10.1088/1367-2630/10/2/025019}, author = {Nest, M. and Remacle, F. and LEVINE, RD} } @article { ISI:000256866700052, title = {Ultrafast vibrational spectroscopy and relaxation in polyatomic molecules: Potential for molecular parallel computing}, journal = {CHEMICAL PHYSICS}, volume = {347}, year = {2008}, month = {MAY 23}, pages = {531-545}, abstract = {The feasibility of controlled ultrafast pumping in the mid IR and the probe of the subsequent intramolecular dynamics is illustrated for vibrational excitation of the two metal carbonyls W(CO)(6) and Mn(CO)(5)Br in solution. Pumping and probing is performed by short, 130 fs, pulses centered at about 2000 cm(-1). Frequency resolved measurements of the time delayed probe pulse are performed. Measured two dimensional spectra are fitted by a kinetic scheme that models the vibrational dynamics. Fast relaxation is solvent induced with the solvent acting also as a heat bath. The (several) probe signals in the experiment can be thought of as the response of a finite state logic machine. This suggests that the molecular machine can act as an ultrafast (petaHertz) processor. The number of internal (memory) states of the machine is determined by the number of vibrational states in the kinetic scheme that can fit the observed relaxation. The number of outputs of the machine is the number of the several different available probe signals. It is shown that the machine is massively parallel because in each (sub ps) time step it produces an entire vector as an output and that each component of the output vector is, by itself, a transform over the input. Beyond that, the machine can produce a (finite number of) different output vectors in sequential time steps. (c) 2008 Elsevier BN. All rights reserved.}, issn = {0301-0104}, doi = {10.1016/j.chemphys.2008.01.015}, author = {Torres, E. A. and KOMPA, KL and Remacle, F. and LEVINE, RD} } @article { ISI:000259760100041, title = {All optical full adder based on intramolecular electronic energy transfer in the rhodamine-azulene bichromophoric system}, journal = {JOURNAL OF PHYSICAL CHEMISTRY C}, volume = {112}, year = {2008}, month = {OCT 9}, pages = {15880-15885}, abstract = {Charge and electronic energy transfer (ET and EET) are well-studied examples whereby different molecules can signal their state from one (the donor, D) to the other (the acceptor, A). The electronic energy transfer from the donor (Rh) to the acceptor (Az) is used to build an all-optical full adder on a newly synthesized bichromophoric molecule Rh-Az. The results are supported and interpreted by a full kinetic simulation. It is found that the optimal design for the implementation of the full adder relies in an essential way on the intramolecular transfer of information from the donor to the acceptor moiety. However, it is not the case that the donor and the acceptor each act as a half adder.}, issn = {1932-7447}, doi = {10.1021/jp804658b}, author = {Kuznetz, Olga and Salman, Husein and Eichen, Yoav and Remacle, F. and LEVINE, RD and Speiser, Shammai} } @article { ISI:000259265100099, title = {Principles of design of a set-reset finite state logic nanomachine}, journal = {JOURNAL OF APPLIED PHYSICS}, volume = {104}, year = {2008}, month = {AUG 15}, abstract = {Pulsed electrical set and reset inputs are used to simulate the temporal action of a finite state machine in a three terminal configuration for a variety of arrangements. The gate electrode is necessary only if it is of interest to tune the tunneling rate and to compensate for background charges. When the output is the current, a source and drain electrodes are required. If the output is determined by measuring charge occupancy, then a single junction suffices. The electron transfer rates are computed from the free energy change for a single electron transfer to or from a quantum dot of size such that only charge quantization matters. For a small enough dot the device could operate at room temperature. An asymmetric configuration of the source and drain favors a longer term time preservation of the memory of the device. An alternative design that operates with the same energetics and kinetic parameters is to pulse the resistance rather than the voltage. (C) 2008 American Institute of Physics.}, issn = {0021-8979}, doi = {10.1063/1.2970060}, author = {Klein, Michael and LEVINE, RD and Remacle, F.} } @article { ISI:000247197500008, title = {Probing ultrafast purely electronic charge migration in small peptides}, journal = {ZEITSCHRIFT FUR PHYSIKALISCHE CHEMIE-INTERNATIONAL JOURNAL OF RESEARCH IN PHYSICAL CHEMISTRY \& CHEMICAL PHYSICS}, volume = {221}, year = {2007}, pages = {647-661}, abstract = {A pump-probe experiment that can examine a pure charge migration on a time scale short compared to the onset of nuclear motion is discussed. The mass spectrometric studies of Schlag et al. suggest that short peptide terminated by an aromatic amino acid are particularly suitable test compounds. The pump pulse needs to ionize the molecule on a time scale short compared to the period of the electronic motion, typically sub-fs. However, ionization occurs preferentially when the electrical field of the light is maximal so that the duration of the pulse envelope can be somewhat longer. Detection by photoelectron spectrometry of the peptide cation, to produce a dication, is shown to be able to probe the electronic rearrangement.}, issn = {0942-9352}, doi = {10.1524/zpch.2007.221.5.647}, author = {Remacle, F. and LEVINE, RD} } @article { ISI:000251291900027, title = {The emergence of a coupled quantum dot array in a doped silicon nanowire gated by ultrahigh density top gate electrodes}, journal = {JOURNAL OF PHYSICAL CHEMISTRY C}, volume = {111}, year = {2007}, month = {DEC 6}, pages = {17852-17860}, abstract = {The electrical characteristics of Si nanowire gated by an array of very closely spaced nanowire gate electrodes are experimentally determined and theoretically modeled. Qualitative and quantitative changes in the transport characteristics of these devices, as a function of gate-array voltage, are described. Experiments are reported for two widths of Si nanowires, 40 and 17 nm, and for a varying number of gate electrodes, all spaced at a pitch of 33 tim. We find that these top nanowire gate electrodes can be utilized to locally deplete the carriers in the underlying Si nanowire and thus define an array of coupled quantum dots along the nanowire. Reproducible Coulomb blockade is observed, and clear diamond features are obtained when the conductance is plotted in the plane of the source-drain and gate voltages. The regularity of the diamond diagrams is imposed by the regularity of the SNAP top gate electrodes. Model computations of the electronic structure starting from a tight-biding Hamiltonian in the atomic basis suggest that the control made possible by the top gate voltage induces the emergence (and reversible submergence) of a coupled quantum dot structure in an otherwise homogenously doped Si nanowire.}, issn = {1932-7447}, doi = {10.1021/jp071353o}, author = {Xu, Ke and Green, Jonathan E. and Heath, J. R. and Remacle, F. and LEVINE, RD} } @article { ISI:000245036000009, title = {The entropy of a single large finite system undergoing both heat and work transfer}, journal = {MOLECULAR PHYSICS}, volume = {105}, year = {2007}, pages = {419-427}, abstract = {Computing the entropy of a system from a single trajectory is discussed when the energy exchange with the environment includes both mechanical and thermal terms. The physical example chosen as an illustration is a cluster of atoms impacting a hard surface. Each atom of the cluster interacts with the smooth surface by a momentum transfer using the hard cube model [ E. K. Grimmelmann, J. C. Tully and M. J. Cardillo, J. Chem. Phys. 72, 1039 ( 1980)]. Because of the thermal motion of the surface atoms the atoms of the cluster rebound from the surface with a ( random) thermal component to their momentum. The change in the internal energy of the cluster has therefore both a mechanical, work, term and a heat transfer and the heat term contributes to the change in entropy of the cluster but the major contribution is the loss of potentially available work.}, issn = {0026-8976}, doi = {10.1080/00268970701225774}, author = {Gross, A. and LEVINE, RD} } @article { ISI:000250665800030, title = {On the feasibility of an ultrafast purely electronic reorganization in lithium hydride}, journal = {CHEMICAL PHYSICS}, volume = {338}, year = {2007}, month = {SEP 25}, pages = {342-347}, abstract = {Excitation of a coherent electronic wave packet, a linear combination of several electronic stationary states, is discussed with a computational example, the A and B low lying excited states of LiH. Such linear combination results in the electron executing a rotation-like motion in the xz plane with a period of 4 fs. The excitation needs to be shorter than this purely electronic reorganization time and yet the mean energy of the photon should be relatively low so that the A and B states are coherently accessed. These two requirements limit the wave form of the few cycle pump pulse. (c) 2007 Elsevier B.V. All rights reserved.}, issn = {0301-0104}, doi = {10.1016/j.chemphys.2007.05.012}, author = {Remacle, F. and Kienberger, Reinhard and Krausz, Ferenc and LEVINE, RD} } @article { ISI:000250644000027, title = {Laser steered ultrafast quantum dynamics of electrons in LiH}, journal = {PHYSICAL REVIEW LETTERS}, volume = {99}, year = {2007}, month = {NOV 2}, abstract = {The response of the electronic system of LiH to a few-cycle strong field is computed by a time-dependent multiconfiguration method using a large, adaptive, basis set. The intensity, pulse duration, polarization, and phase of carrier frequency can all be tuned to steer the motion of the electrons. It is shown possible to, e.g., direct the electrons to move along the Li-H bond or normal to it. By shifting the phase, the electrons can be driven toward the Li nucleus or away from it. When the pulse is polarized not along the bond the result is a rotation of the charge density.}, issn = {0031-9007}, doi = {10.1103/PhysRevLett.99.183902}, author = {Remacle, F. and Nest, M. and LEVINE, RD} } @article { ISI:000245005600067, title = {Time-resolved electrochemical spectroscopy of charge migration in molecular wires: Computational evidence for rich electronic dynamics}, journal = {JOURNAL OF PHYSICAL CHEMISTRY C}, volume = {111}, year = {2007}, month = {FEB 8}, pages = {2301-2309}, abstract = {Electrical conduction through a molecule tethered by thiol bridges between two gold clusters is examined from a time-dependent point of view. The shortest electronic time scale for charge migration is a few femtoseconds transit, which is too swift for coupling to the nuclei, that proceeds by super exchange. An order of magnitude slower transfer occurs sequentially through the lower-in-energy sigma bonds. The electronic structure computations are performed at a high level ab initio density functional theory level where the external electric fields are included as part of the Hamiltonian. The structure computed includes the thiol bridge as well as the gold trimer at either end of the molecule. The results shown in detail are for the saturated dithiohexane -S-(CH2)(6)-S- bridge between the two gold trimers.}, issn = {1932-7447}, doi = {10.1021/jp0658647}, author = {Remacle, F. and LEVINE, RD} } @article { ISI:000245788200006, title = {Towards parallel computing: representation of a linear finite state digital logic machine by a molecular relaxation process}, journal = {EUROPEAN PHYSICAL JOURNAL D}, volume = {42}, year = {2007}, month = {APR}, pages = {49-59}, abstract = {A chemical system displaced not far from equilibrium is shown to offer a physical realization of a linear sequential digital logic machine. The requirement from the system is that its state is described by giving the current values of the concentration of different chemical species. The time evolution is therefore described by a classical master equation. The Landau-Teller process of vibrational relaxation of diatomic molecules in a buffer gas is used as a concrete example where each vibrational level is taken to be a distinct species. The probabilities (= fractional concentrations) of the species of the physicochemical system are transcribed as words composed of letters from a finite alphabet. The essential difference between the finite precision of the logic machine and the seemingly unbounded number of significant figures that could be used to specify a concentration is emphasized. The transcription between the two is made by using modular arithmetic that is, is the arithmetic of congruence. A digital machine corresponding to the vibrational relaxation process is constructed explicitly for the simple case of three vibrational levels. In this exploratory effort we use words of only one letter. Even this is sufficient to achieve an exponentially large number of memory states.}, issn = {1434-6060}, doi = {10.1140/epjd/e2006-00277-9}, author = {Remacle, F. and LEVINE, RD} } @article { ISI:000249501900046, title = {Transcending binary logic by gating three coupled quantum dots}, journal = {NANO LETTERS}, volume = {7}, year = {2007}, month = {SEP}, pages = {2795-2799}, abstract = {Physical considerations supported by numerical solution of the quantum dynamics including electron repulsion show that three weakly coupled quantum dots can robustly execute a complete set of logic gates for computing using three valued inputs and outputs. Input is coded as gating (up, unchanged, or down) of the terminal dots. A nanosecond time scale switching of the gate voltage requires careful numerical propagation of the dynamics. Readout is the charge (0, 1, or 2 electrons) on the central dot.}, issn = {1530-6984}, doi = {10.1021/nl071376e}, author = {Klein, Michael and Rogge, S. and Remacle, F. and LEVINE, RD} } @article { ISI:000236467500180, title = {All-optical digital logic: Full addition or subtraction on a three-state system}, journal = {PHYSICAL REVIEW A}, volume = {73}, year = {2006}, month = {MAR}, abstract = {Stimulated Raman adiabatic passage (STIRAP) is a well-studied pump-probe control scheme for manipulating the population of quantum states of atoms or molecules. By encoding the digits to be operated on as {\textquoteleft}{\textquoteleft}on{\textquoteright}{\textquoteright} or {\textquoteleft}{\textquoteleft}off{\textquoteright}{\textquoteright} laser input signals we show how STIRAP can be used to implement a finite-state logic machine. The physical conditions required for an effective STIRAP operation are related to the physical conditions expected for a logic machine. In particular, a condition is derived on the mean number of photons that represent an on pulse. A finite-state machine computes Boolean expressions that depend both on the input and on the present state of the machine. With two input signals we show how to implement a full adder where the carry-in digit is stored in the state of the machine. Furthermore, we show that it is possible to store the carry-out digit as the next state and thereby return the machine to a state ready for the next full addition. Such a machine operates as a cyclical full adder. We further show how this full adder can equally well be operated as a full subtractor. To the best of our knowledge this is the first example of a nanosized system that implements a full subtraction.}, issn = {1050-2947}, doi = {10.1103/PhysRevA.73.033820}, author = {Remacle, F. and LEVINE, RD} } @article { ISI:000238805600027, title = {Dissociation kinetics of peptide ions}, journal = {JOURNAL OF PHYSICAL CHEMISTRY A}, volume = {110}, year = {2006}, month = {JUL 13}, pages = {8497-8500}, abstract = {The dissociation of peptide ions has been found to have ultrafast components that in many ways are uniquely different from typical unimolecular kinetics. As such, some peptide reactions provide new channels, which do not conform to statistical models of reaction kinetics. When the dissociation rates are in the 100 fs range, they are in a time scale where statistical methods do not yet apply, although molecules that have not yet dissociated will later in time undergo statistical redistribution of their excess energy, which, however, may not lead to noticeable reactivity within the experimental time frames for large peptides and hence are simply dissipative. This work is meant to reconcile the long time statistical results of Lifshitz et al. (2003) with the work of Schlag et al. (1995/6) that suggests an alternate parallel and much faster time scale for dissociation. It is argued that the two sets of results and interpretations augment one another and in fact open up a most interesting new field of peptide kinetics in addition to the unimolecular behavior, which becomes de facto arrested by the shear size of the molecule being unable to find a transition state on any reasonable time scale.}, issn = {1089-5639}, doi = {10.1021/jp055764l}, author = {Schlag, E. W. and Selzle, H. L. and Schanen, P. and Weinkauf, R. and LEVINE, RD} } @article { ISI:000235543600004, title = {Electrical transport in saturated and conjugated molecular wires}, journal = {FARADAY DISCUSSIONS}, volume = {131}, year = {2006}, pages = {45-67}, abstract = {The mechanism for charge transport in dithio molecular wires tethered between two gold electrodes is investigated, using both a steady state and a time-dependent quantum mechanical approach. The interface with the electrodes is modeled by two gold clusters and the electronic structure of the entire Au-n-S-bridge-S-Au-n system is computed ab initio at the DFT level and semi-empirically, with the extended Huckel theory. Current vs. applied bias, I-V, curves are computed using a scattering Landauer-type formalism in a steady state picture. The applied source-drain and gate voltages are included at the ab initio level in the electronic Hamiltonian and found to influence strongly the I-V characteristics. The time evolution of a non stationary electronic wave packet initially localized on a gold atom at one end of the extended system shows that charge transfer proceeds sequentially, by a hopping mechanism, to the opposite end. Analysis of the effective one electron Hamiltonian matrix shows that the sulfur atom endows a resistive character to the Au-C-S junctions. The S atoms are however rather well coupled to both the gold and carbon atoms so that typically the super exchange limit for electron transfer is not reached unless the molecular bridge is saturated and the Fermi window function is narrow.}, issn = {1364-5498}, doi = {10.1039/b505696a}, author = {Remacle, F. and LEVINE, RD} } @article { ISI:000237399900005, title = {An electronic time scale in chemistry}, journal = {PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA}, volume = {103}, year = {2006}, month = {MAY 2}, pages = {6793-6798}, abstract = {Ultrafast, subfemtosecond charge migration in small peptides is discussed on the basis of computational studies and compared with the selective bond dissociation after ionization as observed by Schlag and Weinkauf. The reported relaxation could be probed in real time if the removal of an electron could be achieved on the attosecond time scale. Then the mean field seen by an electron would be changing rapidly enough to initiate the migration. Tyrosine-terminated tetrapeptides have a particularly fast charge migration where in < 1 fs the charge arrives at the other end. A femtosecond pulse can be used to observe the somewhat slower relaxation induced by correlation between electrons of different spins. A slower relaxation also is indicated when removing a deeper-lying valence electron. When a chromophoric amino acid is at one end of the peptide, the charge can migrate all along the peptide backbone up to the N end, but site-selective ionization is probably easier to detect for tryptophan than for tyrosine.}, issn = {0027-8424}, doi = {10.1073/pnas.0601855103}, author = {Remacle, F. and LEVINE, RD} } @article { ISI:000241248400049, title = {A mechanical representation of entropy for a large finite system}, journal = {JOURNAL OF CHEMICAL PHYSICS}, volume = {125}, year = {2006}, month = {OCT 14}, abstract = {The temporal evolution of the entropy of a mechanical system as described by a single trajectory is computed using the Clausius [Philos. Mag. 40, 122 (1868)] equality. This requires computing the maximal work that can be done by the system and comparing it to the actual work performed. A single trajectory suffices to determine the entropy when it is {\textquoteleft}{\textquoteleft}typical,{\textquoteright}{\textquoteright} meaning that average values of mechanical variables will not be different when computed using trajectories with different initial conditions. The results are illustrated for small rare gas clusters heated and compressed by an impact at a hard surface. (c) 2006 American Institute of Physics.}, issn = {0021-9606}, doi = {10.1063/1.2357149}, author = {Gross, A. and LEVINE, RD} } @article { ISI:000242297500064, title = {Mechanical simulation of the pressure and the relaxation to thermal equilibrium of a hot and dense rare gas cluster}, journal = {JOURNAL OF PHYSICAL CHEMISTRY B}, volume = {110}, year = {2006}, month = {NOV 30}, pages = {24070-24076}, abstract = {A cold atomic cluster can be very rapidly heated and compressed by a hypersonic impact at a hard surface. The impact can be simulated by computing a classical trajectory for the motion of the atoms. By suddenly confining the hot and dense cluster within a rigid container, it is possible to monitor the time evolution of the force acting on the faces of the container. It is found that the pressure computed this way very rapidly decays to a time-independent value. After a somewhat longer time, this value reproduces the value for the pressure computed as the sum of the kinetic and internal pressures. This agreement is expected for a system in equilibrium. These observations support the conclusion that there is a fast relaxation to thermal equilibrium in these essentially hard-sphere systems. The deviation from equilibrium is primarily due to the propagation of shock waves within the cluster. The equilibrium pressure can reach up to the megabar range.}, issn = {1520-6106}, doi = {10.1021/jp065765t}, author = {Gross, A. and LEVINE, RD} } @article { ISI:000234520300023, title = {Molecule-based photonically switched half and full adder}, journal = {JOURNAL OF PHYSICAL CHEMISTRY A}, volume = {110}, year = {2006}, month = {JAN 12}, pages = {177-184}, abstract = {A single molecule logic gate using electronically excited states and ionization/fragmentation can take advantage of the differences in cross-sections for one and two photon absorption. Fault tolerant optically pumped half adder and full adder are discussed as applications. A full adder requires two separate additions, and the logic concatenation that is required to implement this is physically achieved by an intramolecular transfer along the side chain of 2-phenylethyl-N,N-dimethylamine (PENNA). Solutions of the kinetic equations for the temporal evolution of the concentration of different states in the presence of time-varying laser fields are used to illustrate the high contrast ratios that are potentially possible for such devices.}, issn = {1089-5639}, doi = {10.1021/jp0557417}, author = {Remacle, F. and Weinkauf, R. and LEVINE, RD} } @article { ISI:000236387700021, title = {Probing electronic rearrangement during chemical reactions}, journal = {PHYSICA SCRIPTA}, volume = {73}, year = {2006}, note = {15th European Conference of Molecular Collisions, Nunspeet, NETHERLANDS, SEP, 2004}, month = {JAN}, pages = {C1-C5}, abstract = {During a chemical reaction the electronic structure of the reactants reforms to the structure of the products. In the simplest case, an old bond is broken and simultaneously a new bond is formed. Even when this change occurs adiabatically, meaning that the electronic charge distribution tracks the motion of the nuclei without change in its quantum state, there is a displacement of charge, particularly so if there is a switch from a covalent to an ionic bonding. This reorganization can be probed by light emitted during the very collision. The F + H(2) reaction is used as a computational example.}, issn = {0031-8949}, doi = {10.1088/0031-8949/73/1/N01}, author = {Kornweitz, H and Gross, A. and Birnbaum, G and LEVINE, RD} } @article { ISI:000241056600057, title = {The time scale for electronic reorganization upon sudden ionization of the water and water-methanol hydrogen bonded dimers and of the weakly bound NO dimer}, journal = {JOURNAL OF CHEMICAL PHYSICS}, volume = {125}, year = {2006}, month = {OCT 7}, abstract = {When the valence molecular orbital is localized sudden ionization can cause the nascent hole to move rapidly even before any relaxation of the geometry occurs. Hydrogen bonded clusters offer suitable test systems where the hole is initially localized on one moiety. Computational studies are reported for the water dimer and water-methanol bimer. The local ionization potential of water is different in the methanol-water and water-methanol conformers and this difference is very clearly reflected in the dynamics of charge migration. For the NO dimer the results are that its structure is symmetric so that the two NO molecules are equivalent and do not exhibit the required localization. The role of symmetry is also evident in the charge propagation for holes created in different orbitals. Localization of the initial hole distribution even if absent in the bare molecule can still be induced by the intense electric field of a sudden photoionization. This effect is computationally studied for the NO dimer in the presence of a static electric field. (c) 2006 American Institute of Physics.}, issn = {0021-9606}, doi = {10.1063/1.2227023}, author = {Remacle, F. and LEVINE, RD} } @article { ISI:000229134000093, title = {The changing landscape of physical chemistry at the beginning of the 21st century}, journal = {JOURNAL OF PHYSICAL CHEMISTRY B}, volume = {109}, year = {2005}, month = {MAY 19}, pages = {9853-9854}, issn = {1520-6106}, doi = {10.1021/jp040754q}, author = {Somorjai, GA and LEVINE, RD} } @article { ISI:000230521900005, title = {A counter based on the electrical input/output stimuli activation of an array of quantum dots}, journal = {CHEMPHYSCHEM}, volume = {6}, year = {2005}, month = {JUL 11}, pages = {1239-1242}, issn = {1439-4235}, doi = {10.1002/cphc.200500057}, author = {Remacle, F. and WILLNER, I and LEVINE, RD} } @article { ISI:000228565200006, title = {Electrical addressing of confined quantum systems for quasiclassical computation and finite state logic machines}, journal = {PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA}, volume = {102}, year = {2005}, month = {APR 19}, pages = {5653-5658}, abstract = {Conduction spectroscopy measures the current I through a nanosystem as a function of the voltage V between two electrodes. The differential conductance, dl/dV, has peaks that can be assigned to resonance conditions with different electronic levels of the system. Between these increments, the current has roughly constant plateaus. We discuss how measurements of the current vs. voltage can be used to perform Boolean operations and hence construct finite state logic machines and combinational circuits. The inputs to the device are the source-drain voltage, including its sign, and a gate voltage applied in a manner analogous to optical Stark spectroscopy. As simple examples, we describe a two-state set-reset machine (a machine whose output depends on the input and also on its present state) and a full adder circuit (a circuit that requires three inputs and provides two outputs).}, issn = {0027-8424}, doi = {10.1073/pnas.0501623102}, author = {Remacle, F. and Heath, J. R. and LEVINE, RD} } @article { ISI:000233353200019, title = {Evanescent high pressure during hypersonic cluster-surface impact characterized by the virial theorem}, journal = {JOURNAL OF CHEMICAL PHYSICS}, volume = {123}, year = {2005}, month = {NOV 15}, abstract = {Matter under extreme conditions can be generated by a collision of a hypersonic cluster with a surface. The ultra-high-pressure interlude lasts only briefly from the impact until the cluster shatters. We discuss the theoretical characterization of the pressure using the virial theorem and develop a constrained molecular-dynamics procedure to compute it. The simulations show that for rare-gas clusters the pressures reach the megabar range. The contribution to the pressure from momentum transfer is comparable in magnitude and is of the same sign as that ({\textquoteright}{\textquoteright}the internal pressure{\textquoteright}{\textquoteright}) due to repulsive interatomic forces. The scaling of the pressure with the reduced mechanical variables is derived and validated with reference to the simulations.}, issn = {0021-9606}, doi = {10.1063/1.2110207}, author = {Gross, A. and LEVINE, RD} } @article { ISI:000232725900025, title = {Temperature-dependent and friction-controlled electrochemically induced shuttling along molecular strings associated with electrodes}, journal = {CHEMPHYSCHEM}, volume = {6}, year = {2005}, month = {OCT 14}, pages = {2179-2189}, abstract = {The temperature and solvent composition dependence of the electrochemically stimulated rate of shuttling of the redox-active cyclophane, cyclobis(paroquat-p-phenylene), on a molecular string has been studied. The molecular string includes a pi-donor diiminebenzene-site that is associated on one side with on electrode, and stoppered on the other side with on adamantane unit. The cyclophone rests on the pi-donor site, owing to stabilizing pi-donor-acceptor interactions. Electrochemical reduction of the cyclophone units, to the bis-radical cation cyclophone, results in the shuttling of the reduced cyclophane towards the electrode, a process that is driven by the removal of the stabilizing donor-acceptor interactions, and the electrostatic attraction of the reduced product by the electrode. The latter process is energetically downhill, and is temperature-independent. Upon oxidation of the reduced cyclophane that is associated with the electrode, the energetically uphill shuttling of the oxidized cyclophane to the pi-donor site proceeds. The rote of this translocation process has been found to be temperature-dependent, and controlled by the solvent composition. The experimental results have been theoretically analyzed in terms of Kramers{\textquoteright} molecular friction model. The theoretical fitting of the experimental results, using solutions of variable composition, reveals that the rate-constants for the uphill reaction in a pure aqueous solution follow the temperature-dependence of the viscosity of water. The results demonstrate the significance of friction phenomena in shuttling processes within molecular machines.}, issn = {1439-4235}, doi = {10.1002/cphc.200500162}, author = {Katz, E and Baron, R and WILLNER, I and Richke, N and LEVINE, RD} } @article { ISI:000187967300020, title = {Electrical transmission of molecular bridges}, journal = {CHEMICAL PHYSICS LETTERS}, volume = {383}, year = {2004}, month = {JAN 15}, pages = {537-543}, abstract = {Transmission of electrons through orbitals of molecules is discussed using high-level ab initio methods that allow an orbital interpretation. The transmission is computed for a molecule tethered between gold atoms. Strong coupling to the gold is achieved using a sulfur atom at each end of the molecule. sigma-type orbitals can conduct as well as conjugated bridges provided that the orbitals have weights on the sulfur atoms. The current depends exponentially on the voltage applied to the molecule and this voltage can also shift the electronic density and further alter the transmission. The conductivity can also be modified by a gate voltage. (C) 2003 Elsevier B.V. All rights reserved.}, issn = {0009-2614}, doi = {10.1016/j.cplett.2003.11.072}, author = {Remacle, F. and LEVINE, RD} } @article { ISI:000187308400050, title = {Updated principle of corresponding states}, journal = {JOURNAL OF CHEMICAL EDUCATION}, volume = {81}, year = {2004}, month = {JAN}, pages = {142-146}, issn = {0021-9584}, author = {Ben-Amotz, D and Gift, AD and LEVINE, RD} } @article { ISI:000223356800019, title = {Electronic and electrical response of arrays of metallic quantum dots}, journal = {INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY}, volume = {99}, year = {2004}, note = {4th Congress of the International-Society-for-Theoretical-Chemical-Physics (ICTCP 4), Natl Youth Inst, Marly Le Roi, FRANCE, JUL 09-16, 2002}, month = {SEP 15}, pages = {743-751}, publisher = {Int Soc Theoret Chem Phys}, abstract = {We study ordered arrays of Quantum Dots (QDs) as model systems for the electronic structure and response of solids and devices built from nanoscale components. QDs self-assemble as two-dimensional solids, with novel optical and electric properties, which can be experimentally tuned. The properties are controlled chemically via the selection of the composition and size of the individual QDs and physically through such external controls as the packing, temperature, and electrical and magnetic fields. The freedom of the architectural design is constrained because even the best synthesis does not yield dots of exactly the same size. We discuss the effects of disorder on the electronic structure of arrays of metallic dots and on their transport properties. (C) 2004 Wiley Periodicals, Inc.}, issn = {0020-7608}, doi = {10.1002/qua.20047}, author = {Remacle, F. and LEVINE, RD} } @article { ISI:000223859800023, title = {Level crossing conductance spectroscopy of molecular bridges}, journal = {APPLIED PHYSICS LETTERS}, volume = {85}, year = {2004}, month = {SEP 6}, pages = {1725-1727}, abstract = {A possible mechanism for negative differential resistance is discussed. The level crossing is induced by the source-drain voltage applied across the bridge. The effect is most dramatic when the zero field levels that are resonant with the electrodes are almost degenerate. It is suggested that such degeneracies can arise often when the junctions on either side are weakly coupled by the bridge. Quantitative results for I-V curves are reported on the basis of high-level electronic structure computations for the junction-bridge-junction region and where the electric field is included in the Hamiltonian. (C) 2004 American Institute of Physics.}, issn = {0003-6951}, doi = {10.1063/1.1791745}, author = {Remacle, F. and LEVINE, RD} } @article { ISI:000225227700005, title = {Nanowiring by molecules}, journal = {JOURNAL OF PHYSICAL CHEMISTRY B}, volume = {108}, year = {2004}, month = {NOV 25}, pages = {18129-18134}, abstract = {Microelectronic sensors require the nanowiring of a selectively active site to an electrode. Different molecules can be used as the bridge that establishes the electrical communication. We report computational results for the current carried by molecules tethered between two gold clusters as a function of the overvoltage. The computations include the effect of the voltage at the ab initio level. The trends are consistent with the currents as measured by electrochemical means and suggest that the rate of charge migration can reach far higher values than measured given somewhat higher applied bias or the application of a gate voltage. The role of polarization of the molecular charge density by the applied voltage can be quite significant with definite propensity for the orientation of the molecular charge density with respect to the field. Conduction spectroscopy is therefore analogous to optical spectroscopy in strong laser fields where the field is not a weak probe but C dresses the system and can be used to control it.}, issn = {1520-6106}, doi = {10.1021/jp047591q}, author = {Remacle, F. and WILLNER, I and LEVINE, RD} } @article { ISI:000223410100034, title = {Quasiclassical computation}, journal = {PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA}, volume = {101}, year = {2004}, month = {AUG 17}, pages = {12091-12095}, abstract = {The chemical kinetic description of time evolution where the phase is random but the states are discrete is discussed as a basis for a computational approach. This proposed scheme uses numbers in the entire range of 0 to 1 to represent Boolean propositions. In the implementation by chemical kinetics these numbers are the mole fractions of different species. Vibrational relaxation in a mixture of HCI and DCI is the physical system that is used to illustrate the approach. Energy exchange in such a mixture corresponds to two strongly coupled two-level systems. A search problem, previously discussed in the quantum computing literature, is solved as an example. The solution requires the same number of function evaluations as in the quantal case. The action of the oracle is described in detail.}, issn = {0027-8424}, doi = {10.1073/pnas.0403871101}, author = {Remacle, F. and LEVINE, RD} } @article { ISI:000224349600043, title = {Systematics of collision-induced light emission from hot matter}, journal = {JOURNAL OF PHYSICAL CHEMISTRY A}, volume = {108}, year = {2004}, month = {OCT 14}, pages = {8949-8953}, abstract = {The hypersonic impact of a molecular cluster at a hard surface generates a hot and compressed globule that in a very short while expands and shatters. Even at impact velocities below the onset of ionization this hot matter has a time varying transient dipole that can emit light. We discuss the spectral range and the power (in absolute units) of the emission spectrum. The computational results for the emission spectrum from our molecular dynamics simulation are compared to extrapolations of experimental results for collision-induced absorption at lower energies. The very short time interval during which the cluster survives intact means that the emitted power is low so options for increasing the yield of photons are discussed.}, issn = {1089-5639}, doi = {10.1021/jp0487915}, author = {Gross, A. and Kjellberg, M and LEVINE, RD} } @article { ISI:000186425000010, title = {Collision-induced IR emission spectra of impact-heated rare-gas clusters}, journal = {JOURNAL OF PHYSICAL CHEMISTRY A}, volume = {107}, year = {2003}, month = {NOV 13}, pages = {9567-9574}, abstract = {Emission spectra of mixed rare gas clusters, heated by impact with a hard surface at hypersonic velocities, are shown to extend into the near-IR and visible regimes. The emission is due to the transient dipole that arises during the collision of dissimilar atoms. The simulations are for a cluster that remains in the electronic ground state throughout the collision and use classical dynamics to determine the positions of the atoms vs time. The spectrum is computed as the Fourier transform of the (quantum mechanical) time rate of change of the dipole of the cluster. The time dependence of the dipole velocity is obtained by replacing the positions of the atoms by the computed classical functions of time. Taking the Fourier transform of the dipole velocity rather than of the dipole itself introduces a quantal correction with the result that the computed spectrum satisfies the oscillator sum rule. Binary collisions make the major contribution to the spectrum and there are hardly any caging effects. The spectral density of emitted photons is found to be thermal with a temperature that scales linearly with the impact velocity. Using the oscillator sum rules, this temperature is related to the deformation energy of the electronic charge cloud of the cluster. The hot cluster shatters and the fragments are in translational thermal equilibrium with a mean energy that scales linearly with the energy of impact. The temperature of the emitted light is, therefore, significantly lower than the translational temperature.}, issn = {1089-5639}, doi = {10.1021/jp0356160}, author = {Gross, A. and LEVINE, RD} } @article { ISI:000187279200022, title = {Gating the conductivity of arrays of metallic quantum dots}, journal = {JOURNAL OF PHYSICAL CHEMISTRY B}, volume = {107}, year = {2003}, month = {DEC 18}, pages = {13892-13901}, abstract = {Experimental and computational studies demonstrating that the conduction of compressed, two-dimensional arrays of hexagonally ordered Ag quantum dots (QDs) may be varied through the influence of applied electric fields are reported and discussed. Monolayers of Ag QDs are incorporated into three-terminal (gated) devices, in which temperature, source-drain voltage (V-sd), gating voltage (V-g), compression of the array, and QD size distribution may all be varied. Experimental and computational results are compared in an effort to construct a physical picture of the system. Current vs V-sd plots at low temperatures exhibit systematic nonlinearities that change over to an ohmic-like behavior at higher temperatures and/or higher V-sd. The voltage-induced transition is discussed as a transition of the conducting states from domain localized to delocalized. Such a transition was previously observed in the temperature dependence of the resistance. The computational model reveals that this transition is also highly sensitive to both the compression of the array and the size-distribution of the dots. We calculate the influence of V-g on the conductivity of the QD array, using the same computational model. In both the experiment and the model, we find a significant voltage gating effect and we observe hole-type conductivity of the array. Overall, the results demonstrate that low-temperature transport measurements provide a spectroscopic-like probe of the electronic states of the QD lattice. The theoretical approach further suggests that quite different gating behavior can be observed for electrodes with a different Fermi energy than the gold electrodes used in the experiment.}, issn = {1520-6106}, doi = {10.1021/jp036357h}, author = {Remacle, F. and Beverly, KC and Heath, J. R. and LEVINE, RD} } @article { ISI:000184675600021, title = {Spectroscopic characterization of collision-induced electronic deformation energy using sum rules}, journal = {JOURNAL OF CHEMICAL PHYSICS}, volume = {119}, year = {2003}, month = {AUG 22}, pages = {4283-4293}, abstract = {Collision induced spectra allow a characterization of the rate of change of the dipolar asymmetry of the electronic charge distribution. We compute such spectra using classical trajectories but include essential quantal corrections. These corrections are necessary to satisfy the sum rules to leading order in Planck{\textquoteright}s constant. A corrected computation using classical dynamics for the motion during the collision results when the spectrum is computed from the dipole velocity rather than from the dipole itself. The resulting spectrum is then an asymmetric function of frequency. The Laplace distribution is discussed as a convenient representation of the asymmetric spectrum over both the negative and positive frequency axis. For the emission spectrum the frequency distribution corresponds to the Planck equation with a radiation temperature that is equal to the mean deformation energy of the electronic charge distribution. Therefore, collision induced emission provides a thermometer for the electronic deformation during the collision. (C) 2003 American Institute of Physics.}, issn = {0021-9606}, doi = {10.1063/1.1592510}, author = {Gross, A. and LEVINE, RD} } @article { ISI:000183931400022, title = {Ultra-short time resolution from energy-dependent interference of photodissociation amplitudes}, journal = {CHEMICAL PHYSICS LETTERS}, volume = {375}, year = {2003}, month = {JUN 25}, pages = {141-148}, abstract = {Measuring the wavelength dependence of photodissociation transition amplitudes to crossing electronic states is discussed with reference to extracting time domain information. Outwards from the crossing the system evolves on one or the other state as ascertained from the electronic state of the products. One can therefore measure the phase difference for the motion on the two potentials accumulated between the Franck-Condon region and the crossing point. A computational example, the photodissociation of HI and DI, is provided. The interference varies rapidly with wavelength and provides considerable leverage for determination of ultra-short time differences. The interference exhibits a significant isotope effect. (C) 2003 Elsevier Science B.V. All rights reserved.}, issn = {0009-2614}, doi = {10.1016/S0009-2614(03)00850-9}, author = {Torres, E. A. and Baugh, DA and LEVINE, RD} } @article { ISI:000183557300045, title = {Voltage-induced phase transition in arrays of metallic nanodots: Computed transport and surface potential structure}, journal = {APPLIED PHYSICS LETTERS}, volume = {82}, year = {2003}, month = {JUN 23}, pages = {4543-4545}, abstract = {Computed dc transport in compressed arrays of metallic quantum dots exhibits a voltage-induced phase transition at low temperatures. The transition is seen in the temperature dependence of the conductance at different voltages: from a variable hopping dependence at low voltage to an ohmic, activated behavior at higher voltages. The computations also exhibit the transition as a break in the current versus voltage plots at low temperatures where, at higher voltages, the plot is linear. At higher temperatures, the conductance is ohmic. A many-electron basis is used. The same transition is seen in the surface potential contours. (C) 2003 American Institute of Physics.}, issn = {0003-6951}, doi = {10.1063/1.1583871}, author = {Remacle, F. and LEVINE, RD} } @article { ISI:000183532000016, title = {Current-voltage-temperature characteristics for 2D arrays of metallic quantum dots}, journal = {ISRAEL JOURNAL OF CHEMISTRY}, volume = {42}, year = {2002}, pages = {269-280}, abstract = {Computational results for the temperature-dependent conductivity of compressed arrays of size-selected Ag nanodots are discussed. Special attention is given to the role of phase transitions of the array as a function of external control variables: the applied voltage, the temperature, and the compression of the array. The computations are based on a scattering formalism that is presented in detail so that all the assumptions are explicitly spelled out. The results demonstrate the ability of low-lying excited electronic states of 2D lattices to probe by temperature-dependent conductivity measurements.}, issn = {0021-2148}, doi = {10.1560/N79E-63LC-UK4Y-MQQ6}, author = {Remacle, F. and LEVINE, RD} } @article { ISI:000176387300008, title = {Cluster-cluster fusion}, journal = {COMPTES RENDUS PHYSIQUE}, volume = {3}, year = {2002}, month = {APR}, pages = {341-352}, abstract = {An experimental study of molecular fusion in fullerene-fullerene collisions is presented and the theoretical interpretation of the cross section is reconsidered in terms of phase space arguments and competition with direct collision induced dissociation. The form and absolute magnitude of the cross sections for C60+ + C-70 (or C-70(+) + C-60) and C-70(+) + C-70 can be understood, however, the much smaller cross section for C-60(+)+ C-60 remains a puzzle. The fragmentation behaviour of the hot fusion product is well described by a maximal entropy model indicating equipartition of the centre of mass collision energy followed by statistical fragmentation. (C) 2002 Academie des sciences/Editions scientifiques et medicales Elsevier SAS.}, issn = {1631-0705}, doi = {10.1016/S1631-0705(02)01323-3}, author = {Campbell, EEB and Glotov, AV and Lassesson, A and LEVINE, RD} } @article { ISI:000175169700014, title = {Conductivity of 2-D Ag quantum dot arrays: Computational study of the role of size and packing disorder at low temperatures}, journal = {JOURNAL OF PHYSICAL CHEMISTRY B}, volume = {106}, year = {2002}, month = {APR 25}, pages = {4116-4126}, abstract = {The temperature dependence of the coherent DC conductivity of an Ag quantum dot (QD) monolayer has been computed allowing for size fluctuations of the QDs as well as for packing disorder. The computation uses a scattering formalism with an electron exchange coupling for adjacent QDs. The strength of this coupling can be tuned by compression of the array, and the same coupling is used as previously deter-mined from second harmonic generation spectroscopy of such monolayers. To agree with the experimental results, the computations center attention on the regime of not fully compressed arrays, when the exchange coupling does not fully mask the role of disorder. At very low disorder and/or at higher compressions. the computations show a phase transition to a fully delocalized conducting regime. At very low temperatures, the computed conductivity increases with temperature as exp(-2(E-0/kT)(1/2)). The characteristic energy Eo is found to be a measure of the effective coupling of next-nearest neighbors, suggesting that conduction occurs by variable range charge hopping or, in the language of electron transfer, by super-exchange, At higher temperatures, there is a crossover to an activated regime, exp(-(E-a/kT)), where the activation energy E. is shown to be a measure of the mean excess energy of the moving charges. The transition temperature to activated conduction scales with the extent of disorder. The increase of conductivity with temperature is interpreted as reflecting a gap in the density of conducting states for energies just above the ground electronic state of the array.}, issn = {1520-6106}, doi = {10.1021/jp013937a}, author = {Remacle, F. and Beverly, KC and Heath, J. R. and LEVINE, RD} } @article { ISI:000174676400006, title = {Driving high threshold chemical reactions during the compression interlude in cluster surface impact}, journal = {CHEMICAL PHYSICS LETTERS}, volume = {354}, year = {2002}, month = {MAR 18}, pages = {395-402}, abstract = {Molecular-dynamics simulations of a cluster impacting a hard surface show that, initially, the cluster is rapidly compressed and translationally heated. During this short but distinct stage, the cluster is a suitable medium for chemistry: the number of layers of the cluster is not changing; the constituents of the cluster can collide several times and both bimolecular and collisionally driven unimolecular reactions can occur. Hypersonic velocities of impact are needed for a considerable temperature rise. Following compression, the cluster fragments by expanding into a hemispheroidal plume. For supersonic impact. the cluster expands nearer to the surface forming an oblate, omelet-like, hemispheroid. (C) 2002 Elsevier Science B.V. All rights reserved.}, issn = {0009-2614}, doi = {10.1016/S0009-2614(02)00150-1}, author = {Gross, A. and Kornweitz, H and Raz, T and LEVINE, RD} } @article { ISI:000173687600010, title = {Imaging transport disorder in conducting arrays of metallic quantum dots: an experimental and computational study}, journal = {ADVANCED MATERIALS}, volume = {14}, year = {2002}, month = {JAN 16}, pages = {124+}, abstract = {Surface potential imaging (see Figure) reveals the transition to collective behavior in a two-dimensional quantum dot solid. As described in this communication, an electrical potential gradient is applied across the film, and various scanning probe and electron microscopy images are correlated to interrogate the role of disorder in the transition from local to collective behavior.}, issn = {0935-9648}, doi = {10.1002/1521-4095(20020116)14:2<124::AID-ADMA124>3.0.CO;2-N}, author = {Sample, JL and Beverly, KC and Chaudhari, PR and Remacle, F. and Heath, J. R. and LEVINE, RD} } @article { ISI:000177107000022, title = {Molecular logic by optical spectroscopy with output transfer by charge migration along a peptide}, journal = {CHEMICAL PHYSICS}, volume = {281}, year = {2002}, month = {AUG 1}, pages = {363-372}, abstract = {Computing on the (sub) nanoscale is discussed and illustrated by a specific example of charge transfer along a molecular frame. The general research program is to implement an entire finite state logic machine on a molecule. It is proposed to do so in stages. The first stage is to implement Boolean logic circuits on a single molecule. This has already been achieved up to the level of a full adder. Our current work seeks to implement even more elaborate circuits, to go beyond Boolean logic gates and to go beyond combinational logic circuits to the level of sequential machines. In the longer run it will be necessary to concatenate logical units so that a molecule-like assembly is needed. Here we show by a concrete experimental example that intramolecular concatenation is possible: The molecular backbone is used to move information between two ends of a short peptide. The experiment is a gas phase laser excitation of a molecule with an aromatic chromophore at one end. The absorption by the chromophore localizes the initial excitation. Different outcomes are possible depending on additional inputs. Specifically, charge can be made to migrate to the other end of the molecule. (C) 2002 Elsevier Science B.V. All rights reserved.}, issn = {0301-0104}, doi = {10.1016/S0301-0104(02)00448-2}, author = {Remacle, F. and Weinkauf, R. and Steinitz, D and KOMPA, KL and LEVINE, RD} } @article { ISI:000175483900003, title = {Quantum dot artificial solids: Understanding the static and dynamic role of size and packing disorder}, journal = {PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA}, volume = {99}, year = {2002}, month = {APR 30}, pages = {6456-6459}, abstract = {This perspective examines quantum dot (QD) superlattices as model systems for achieving a general understanding of the electronic structure of solids and devices built from nanoscale components. QD arrays are artificial two-dimensional solids, with novel optical and electric properties, which can be experimentally tuned. The control of the properties is primarily by means of the selection of the composition and size of the individual QDs and secondly, through their packing. The freedom of the architectural design is constrained by nature insisting on diversity. Even the best synthesis and separation methods do not yield dots of exactly the same size nor is the packing in the self-assembled array perfectly regular. A series of experiments, using both spectroscopic and electrical probes, has characterized the effects of disorder for arrays of metallic dots. We review these results and the corresponding theory. In particular, we discuss temperature-dependent transport experiments as the next step in the characterization of these arrays.}, issn = {0027-8424}, doi = {10.1073/pnas.251537898}, author = {Beverly, KC and Sample, JL and Sampaio, JF and Remacle, F. and Heath, J. R. and LEVINE, RD} } @article { ISI:000209010600003, title = {Real-space renormalization group study of the Hubbard model on a non-bipartite lattice}, journal = {INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES}, volume = {3}, year = {2002}, month = {JAN}, pages = {4-16}, abstract = {We present the real-space block renormalization group equations for fermion systems described by a Hubbard Hamiltonian on a triangular lattice with hexagonal blocks. The conditions that keep the equations from proliferation of the couplings are derived. Computational results are presented including the occurrence of a first-order metal-insulator transition at the critical value of U/t approximate to 12.5.}, issn = {1422-0067}, doi = {10.3390/i3010004}, author = {Wang, JX and Kais, Sabre and LEVINE, RD} } @article { ISI:000173492000004, title = {On spectroscopy, control, and molecular information processing}, journal = {CHEMPHYSCHEM}, volume = {3}, year = {2002}, month = {JAN 18}, pages = {43-51}, abstract = {Implementing a logic machine on a single molecule was recently discussed with experimental roadmarks. Lasers were used to control the input and sometimes also the output of information with additional processing done via inter- and intramolecular dynamics. We examine the special requirements for an experiment that mimics a logic circuit. We use two-photon processes as physical examples of our considerations and discuss both combinational and sequential logic machines.}, issn = {1439-4235}, doi = {10.1002/1439-7641(20020118)3:1<43::AID-CPHC43>3.0.CO;2-4}, author = {Steinitz, D and Remacle, F. and LEVINE, RD} } @article { ISI:000176827500005, title = {Voltage-induced nonlinear characteristics of arrays of metallic quantum dots}, journal = {NANO LETTERS}, volume = {2}, year = {2002}, month = {JUL}, pages = {697-701}, abstract = {We show by computations that even low voltages can significantly modify the electronic states of a small compressed array of metallic quantum dots. This is because the voltage counteracts the effects of inherent disorder on the wave function. The low-lying excitations can be thermally probed. At lower voltages the array breaks into islands that are superexchange coupled. At higher voltages the response is ohmic, then it cuts out due to formation of a junction layer.}, issn = {1530-6984}, doi = {10.1021/nl025571z}, author = {Remacle, F. and LEVINE, RD} } @article { ISI:000177574400003, title = {Improved corresponding states scaling of the equations of state of simple fluids}, journal = {JOURNAL OF CHEMICAL PHYSICS}, volume = {117}, year = {2002}, month = {SEP 8}, pages = {4632-4634}, abstract = {The principle of corresponding states is re-examined in the light of recent experimental and theoretical fluid equation of state data compilations. The results are used to critically test and extend the fundamental concept of corresponding states scaling for simple fluids (including rare gases, diatomics and methane). Classical corresponding states scaling based on critical point constants is found to produce weaker universal behavior than a new scaling procedure linked directly to the two intermolecular interaction potential parameters of a Lennard-Jones-6-12 fluid. The improved universal behavior revealed using this Lennard-Jones-corresponding-states scaling may either reflect inaccuracies in previous critical constant estimates, or perhaps point to more fundamental differences between the critical properties of different fluids. (C) 2002 American Institute of Physics.}, issn = {0021-9606}, doi = {10.1063/1.1503775}, author = {Ben-Amotz, D and Gift, AD and LEVINE, RD} } @article { ISI:000179921100001, title = {Size effects in the electronic properties of finite arrays of exchange-coupled quantum dots}, journal = {JOURNAL OF PHYSICAL CHEMISTRY B}, volume = {106}, year = {2002}, month = {DEC 19}, pages = {12847-12850}, abstract = {Transport properties of arrays of metallic quantum dots are governed by the distance-dependent exchange coupling between the dots. It is shown that the effective value of the exchange coupling, as measured by the charging energy per dot, depends monotonically on the size of the array. The effect saturates for-hexagonal arrays of over 7(5) unit cells. The discussion uses a multistage block renormalization group approach applied to the Hubbard Hamiltonian. A first-order phase transition occurs upon compression of the lattice, and the size dependence is qualitatively different for the two phases.}, issn = {1520-6106}, doi = {10.1021/jp026452a}, author = {Wang, JX and Kais, S and Remacle, F. and LEVINE, RD} } @article { ISI:000167766600031, title = {Electron-nuclear coupling in the classical limit for the electronic degrees of freedom}, journal = {JOURNAL OF PHYSICAL CHEMISTRY A}, volume = {105}, year = {2001}, month = {MAR 29}, pages = {2708-2715}, abstract = {The use of a classical limit for the electronic degrees of freedom avoids the need to keep the nuclei clamped while solving for the dynamics of the electrons. The Hamiltonian for the electrons will then depend on the nuclear coordinates as dynamical variables. The resulting (classical) electron-nuclear coupled equations of motion exhibit dynamical symmetry and are shown to depend only on the ratio, kappa (-4), of the electron to nuclear mass, We explore the coupled electron-nuclear dynamics as a function of kappa for the special case of a single electron moving between two centers. Ln the dynamical regime where the nuclei are heavy and the Born-Oppenheimer separation should work, the full dynamical procedure is in excellent agreement with the nuclear dynamics as computed using the Born-Oppenheimer separation. In the opposite regime where the period of the electronic motion is long, a case that can be physically realized for very high Rydberg states, one reaches an {\textquoteleft}inverse{\textquoteright} behavior where the nuclei adiabatically adjust to the slow electronic motion. The failure of the Born-Oppenheimer separation, as judged by the electronic coupling not being governed solely by the instantaneous position of the nuclei, is more severe when the initial electronic state is not stationary.}, issn = {1089-5639}, doi = {10.1021/jp0042922}, author = {Remacle, F. and LEVINE, RD} } @article { ISI:000167346200047, title = {How large is {\textquoteleft}large{\textquoteright} for a thermodynamic-like behavior}, journal = {PHYSICA E}, volume = {9}, year = {2001}, note = {International Workshop and Seminar on Dynamics of Complex Systems, MAX PLANCK INST PHYS COMPLEX SYST, DRESDEN, GERMANY, MAR 31-JUN 15, 1999}, month = {MAR}, pages = {591-599}, abstract = {It is sometimes stated that in order to be amenable to a simple statistical description. a system needs to have many coupled degrees of freedom. In this view, the statistical limit is to be understood from the dynamics. Here we discuss a complementary point of view where the role of {\textquoteleft}size{\textquoteright} is to ensure that the probabilities of simple events, which are technically marginal probabilities, settle down to a canonical distribution, conditioned by additive constants of the motion. The requirement that the conditioning is on additive variables plays an essential technical role and it is not dear that this condition can be relaxed. In the view discussed here, the effective {\textquoteleft}size{\textquoteright} is determined by the variance of the physical variables of interest. Implications for Monte Carlo sampling are also discussed, with examples. (C) 2001 Elsevier Science B.V. All rights reserved.}, issn = {1386-9477}, doi = {10.1016/S1386-9477(00)00267-8}, author = {LEVINE, RD} } @article { ISI:000169706000030, title = {IR-UV double-resonance photodissociation of nitric acid (HONO2) viewed as molecular information processing}, journal = {ANGEWANDTE CHEMIE-INTERNATIONAL EDITION}, volume = {40}, year = {2001}, pages = {2512+}, issn = {1433-7851}, doi = {10.1002/1521-3773(20010702)40:13<2512::AID-ANIE2512>3.0.CO;2-I}, author = {Witte, T and Bucher, C and Remacle, F. and Proch, D and KOMPA, KL and LEVINE, RD} } @article { ISI:000167521300010, title = {Logic gates using high Rydberg states}, journal = {PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA}, volume = {98}, year = {2001}, month = {MAR 13}, pages = {2973-2978}, abstract = {Connected logic gates can be operated on the levels of one molecule by making use of the special properties of high Rydberg states, Explicit experimental results for the NO molecule are provided as an example. A number of other options, including that of several gates concatenated so as to operate as a full adder, are discussed. Specific properties of high Rydberg states that are used are: their autoionization is delayed so that they can be distinguished from direct multiphoton ionization, during their long life such states also can decay by energy transfer to the molecular core in a way that can be controlled by the judicious application of very weak external electrical fields, and the Rydberg states can be detected by the application of an ionizing electrical field. The combination of two (or three) color photons with and without external weak fields allows the construction of quite elaborate logic circuit diagrams and shows that taking advantage of the different intramolecular dynamics of levels that differ by their excitation enables the compounding of logic operations on one molecular frame.}, issn = {0027-8424}, doi = {10.1073/pnas.061019998}, author = {Remacle, F. and Schlag, E. W. and Selzle, H and KOMPA, KL and Even, U and LEVINE, RD} } @article { ISI:000166485300011, title = {A molecular logic gate}, journal = {PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA}, volume = {98}, year = {2001}, month = {JAN 16}, pages = {410-414}, abstract = {We propose a scheme for molecule-based information processing by combining well-studied spectroscopic techniques and recent results from chemical dynamics. Specifically it is discussed how optical transitions in single molecules can be used to rapidly perform classical (Boolean) logical operations. In the proposed way, a restricted number of states in a single molecule can act as a logical gate equivalent to at least two switches. it is argued that the four-level scheme can also be used to produce gain, because it allows an inversion, and not only a switching ability. The proposed scheme is quantum mechanical in that it takes advantage of the discrete nature of the energy revers but we here discuss the temporal evolution, with the use of the populations only. On a longer time range we suggest that the same scheme could be extended to perform quantum logic, and a tentative suggestion, based on an available experiment, is discussed. We believe that the pumping can provide a partial proof of principle, although this and similar experiments were not interpreted thus far in our terms.}, issn = {0027-8424}, doi = {10.1073/pnas.98.2.410}, author = {KOMPA, KL and LEVINE, RD} } @article { ISI:000168286500002, title = {Quantum dots as chemical building blocks: Elementary theoretical considerations}, journal = {CHEMPHYSCHEM}, volume = {2}, year = {2001}, month = {JAN 19}, pages = {20-36}, abstract = {Quantum dots are clusters of atoms (or molecules) that are small enough that their electronic states are discrete. They can be prepared with a variety of compositions and covering ligands but Bare not quite identical. In particular, the dots will have a variable size. The study of the properties of individual dots is an active subject in its own right. Here we examine the electronic structure of assemblies of dots, where the dots are near enough that they interact. For the purpose of an elementary discussion, metallic dots are regarded as {\textquoteleft}{\textquoteleft}atoms{\textquoteright}{\textquoteright} with one valence orbital. The key point is at they are {\textquoteleft}{\textquoteleft}designer{\textquoteright}{\textquoteright} atoms because their electronic properties be controlled through the synthetic method that is used to prepare the dots. Of direct concerns to us are the size of the dot and the nature of the ligands used to passivate the dots so that they do not coalesce. An important parameter is the energy cost, I, of adding an electron to a dot. The large size of the dots means that, unlike ordinary atoms, the Coulomb repulsion of the added electron is low. Other experimental control parameters are externally applied and include the ability to compress an assembly S of dots, and thereby change the distance between them, or to subject them to static or alternating electromagnetic fields. The response to spectral probes:for the electronic structure is discussed with special emphasis on: new features, such as the onset of conjugation or the insulator-to-metallic transition made accessible by the low charging energy of the dots. We propose a-phased diagram of electronic isomers that can be: accessed under realistic conditions.}, issn = {1439-4235}, doi = {10.1002/1439-7641(20010119)2:1<20::AID-CPHC20>3.3.CO;2-I}, author = {Remacle, F. and LEVINE, RD} } @article { ISI:000167650700010, title = {Superexchange, localized, and domain-localized charge states for intramolecular electron transfer in large molecules and in arrays of quantum dots}, journal = {JOURNAL OF PHYSICAL CHEMISTRY B}, volume = {105}, year = {2001}, month = {MAR 22}, pages = {2153-2162}, abstract = {Superexchange is a longer-range electron-transfer mediated by a nonresonant bridge between the donating and accepting states. We discuss a coupled set of donor/acceptor levels that are not resonant, with special reference to coupling of intermediate strengths. Examples of such systems are peptide cations or arrays of quantum dots. If the coupling is strong enough to overcome the gaps, charge can migrate. If the coupling is too weak, the charge remains localized. In the intermediate case, the charge is shown to be localized over a finite, connected, subset of sites. Degenerate perturbation theory provides a suitable zero-order basis for this intermediate regime. In a time dependent language, in the domain-localized regime, the charge migrates over a limited range of states. Also discussed is an effect of electron correlation, the so-called Coulomb blockade, on charge localization with computational examples. The experimental probing of the domain-localized regime is considered. Probes of the energy dependence of the local density of states such as scanning tunneling microscopy (STM) of arrays of quantum dots and photoelectron spectroscopy (PES) of chromophore bearing molecules are suggested.}, issn = {1089-5647}, doi = {10.1021/jp002972z}, author = {Remacle, F. and LEVINE, RD} } @article { ISI:000169909300011, title = {On the capture cross-section for charge neutralization, recombination, photoassociation and other barrierless reactions}, journal = {CHEMICAL PHYSICS}, volume = {270}, year = {2001}, month = {JUL 15}, pages = {129-132}, abstract = {The collision energy dependence of cross-section for reactions where the reactants attract is discussed. Examples include charge recombination A(+) + B- {\textendash}> products, ion-molecule reactions and other curve crossing processes. The common characteristic of such processes is that on physical grounds there is a critical distance d where capture occurs. Special attention is given to the case where the critical separation is independent of energy and/or impact parameter. A modern example where this is the case is laser-induced association of atoms. The capture cross-section has the functional form sigma = pid(2) (1 - Vg(d)/E-T) where for the collisions discussed the potential is attractive, V-g(d) < 0. Such a cross-section is a decreasing function of the collision energy ET. The same functional form is also useful if the potential is repulsive, V-g(d) > 0. For this well-known case, the cross-section is an increasing function of the collision energy. (C) 2001 Elsevier Science B.V. All rights reserved.}, issn = {0301-0104}, doi = {10.1016/S0301-0104(01)00396-2}, author = {LEVINE, RD} } @article { ISI:000168998000001, title = {On the crossing of electronic energy levels of diatomic molecules at the large-D limit}, journal = {JOURNAL OF CHEMICAL PHYSICS}, volume = {114}, year = {2001}, month = {JUN 8}, pages = {9697-9705}, abstract = {Analytical and numerical results are presented for the intersection of electronic energies of the same space symmetry for electrons in the field of two Coulomb centers in D-dimensions. We discuss why such crossings are allowed and may be less {\textquoteleft}{\textquoteleft}exceptional{\textquoteright}{\textquoteright} than one could think because even for a diatomic molecule there is more than one parameter in the electronic Hamiltonian. For a one electron diatomic molecule at the large-D limit, the electronic energies are shown analytically to diverge quadratically from the point of their intersection. The one electron two Coulomb centers problem allows a separation of variables even when the charges on the two centers are not equal. The case of two electrons, where their Coulombic repulsion precludes an exact symmetry, is therefore treated in the large-D limit. It is then found that, in addition to the quadratic intersection, there is also a curve crossing where the energies diverge linearly. (C) 2001 American Institute of Physics.}, issn = {0021-9606}, doi = {10.1063/1.1372181}, author = {Shi, QC and Kais, S and Remacle, F. and LEVINE, RD} } @article { ISI:000169976000005, title = {Electronic isomerism: Symmetry breaking and electronic phase diagrams for diatomic molecules at the large-dimension limit}, journal = {CHEMPHYSCHEM}, volume = {2}, year = {2001}, month = {JUL 16}, pages = {434-442}, abstract = {We present symmetry-breaking and electronic-structure phase diagrams for two-center molecules with one and two electrons in the limit of a space of large dimensions. For one electron, the phase diagram in the internuclear distance-nuclear charge (R-Z) plane has two different stable phases. One corresponds to the electron equidistant from the two nuclei; the other where the electron is localized on one of the nuclei. The phase diagram for two electrons with two equally charged centers shows three different stable phases corresponding to different electronic-structure configurations. This phase diagram is characterized by a bicritical point. When the charges are unequal, the phase diagram shows only two stable phases, covalent and ionic. This phase diagram is characterized by a tricritical point, where the first-order transition line meets with the second-order transition line. The role of the inter-electron Coulombic repulsion in giving rise to different electronic structures and the distinction between a continuous deformation of one structure into another versus a discontinuous, so-called first-order, transition, where two isomers can coexist, are emphasized. The connection to the spectroscopic notion of intersecting potential energy curves is discussed.}, issn = {1439-4235}, doi = {10.1002/1439-7641(20010716)2:7<434::AID-CPHC434>3.0.CO;2-J}, author = {Shi, QC and Kais, S and Remacle, F. and LEVINE, RD} } @article { ISI:000173040800020, title = {Excitation of Rydberg series in C-60}, journal = {PHYSICAL REVIEW LETTERS}, volume = {87}, year = {2001}, month = {DEC 31}, abstract = {Rydberg series of C-60 are reported for the first time. The Rydberg states are seen in photoelectron spectra using ultrashort pulsed-laser excitation, where the excited states formed are ionized with one further photon from the same laser pulse. The structure is observed for pulse durations as short as 100 fs with indications of residual structure for even shorter pulse excitation. The production mechanism is discussed and the Rydberg states are modeled by analytically solving the Schrodinger equation with a simple jelliumlike potential for C-60.}, issn = {0031-9007}, doi = {10.1103/PhysRevLett.87.273401}, author = {Boyle, M and Hoffmann, K and Schulz, CP and Hertel, IV and LEVINE, RD and Campbell, EEB} } @article { ISI:000169371500002, title = {Intermolecular and intramolecular logic gates}, journal = {JOURNAL OF PHYSICAL CHEMISTRY B}, volume = {105}, year = {2001}, month = {JUN 21}, pages = {5589-5591}, abstract = {Logic circuits operating on different molecules or on different parts of the same molecule can be connected. As an example, a circuit known as a full adder is described. It is made up of two circuits, a half adder on a donor (rhodamine 6G) and another half adder on an acceptor (azulene). The signal, (an intermediate sum), is moved from donor to acceptor by electronic energy transfer. The concatenated logic arrangement is described, and potential applications using other bichromophoric molecules are outlined. Polychromophoric molecules will allow a fanout operation.}, issn = {1089-5647}, doi = {10.1021/jp0101211}, author = {Remacle, F. and Speiser, S and LEVINE, RD} } @article { ISI:000169352300001, title = {Towards a molecular logic machine}, journal = {JOURNAL OF CHEMICAL PHYSICS}, volume = {114}, year = {2001}, month = {JUN 15}, pages = {10239-10246}, abstract = {Finite state logic machines can be realized by pump-probe spectroscopic experiments on an isolated molecule. The most elaborate setup, a Turing machine, can be programmed to carry out a specific computation. We argue that a molecule can be similarly programmed, and provide examples using two photon spectroscopies. The states of the molecule serve as the possible states of the head of the Turing machine and the physics of the problem determines the possible instructions of the program. The tape is written in an alphabet that allows the listing of the different pump and probe signals that are applied in a given experiment. Different experiments using the same set of molecular levels correspond to different tapes that can be read and processed by the same head and program. The analogy to a Turing machine is not a mechanical one and is not completely molecular because the tape is not part of the molecular,machine. We therefore also discuss molecular finite state machines, such as sequential devices, for which the tape is not part of the machine. Nonmolecular tapes allow for quite long input sequences with a rich alphabet (at the level of 7 bits) and laser pulse:shaping experiments provide concrete examples. Single molecule spectroscopies show that a single molecule can be repeatedly cycled through a logical operation. (C) 2001 American Institute of Physics.}, issn = {0021-9606}, doi = {10.1063/1.1372765}, author = {Remacle, F. and LEVINE, RD} } @article { ISI:000084873100009, title = {Architecture with designer atoms: Simple theoretical considerations}, journal = {PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA}, volume = {97}, year = {2000}, month = {JAN 18}, pages = {553-558}, abstract = {{{The distinct electronic states of assemblies of metallic quantum dots are discussed in a simple approximation where each dot is mimicked as an {\textquoteleft}{\textquoteleft}atom{\textquoteright}{\textquoteright} that carries one valence electron. Because of their large size, the charging energy of the dots}, issn = {0027-8424}, doi = {10.1073/pnas.97.2.553}, author = {Remacle, F. and LEVINE, RD} } @article { ISI:000085633200004, title = {On a classical limit for electronic degrees of freedom that satisfies the Pauli exclusion principle}, journal = {PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA}, volume = {97}, year = {2000}, month = {FEB 29}, pages = {1965-1969}, abstract = {Fermions need to satisfy the Pauli exclusion principle: no two can be in the same state. This restriction is most compactly expressed in a second quantization formalism by the requirement that the creation and annihilation operators of the electrons satisfy anti-commutation relations. The usual classical limit of quantum mechanics corresponds to creation and annihilation operators that satisfy commutation relations, as for a harmonic oscillator. We discuss a simple classical limit for Fermions. This limit is shown to correspond to an anharmonic oscillator, with just one bound excited state. The vibrational quantum number of this anharmonic oscillator, which is therefore limited to the range 0 to 1, is the classical analog of the quantum mechanical occupancy. This interpretation is also true for Bosons, except that they correspond to a harmonic oscillator so that the occupancy is from 0 up. The formalism is intended to be useful for simulating the behavior of highly correlated Fermionic systems, so the extension to many electron states is also discussed.}, issn = {0027-8424}, doi = {10.1073/pnas.97.5.1965}, author = {LEVINE, RD} } @article { ISI:000089139900005, title = {On the classical limit for electronic structure and dynamics in the orbital approximation}, journal = {JOURNAL OF CHEMICAL PHYSICS}, volume = {113}, year = {2000}, month = {SEP 15}, pages = {4515-4523}, abstract = {The classical limit is shown to provide a description exactly equivalent to the quantum mechanical one in the approximation where each electron is assigned to an orbital. Strictly speaking it is therefore not a limit but an alternative way of solving the problem. There are some merits of this reformulation, most notably in that it brings the phase of the orbitals to the forefront, on equal footing as the occupancies. This allows one to discuss, e.g., electron localization, in a clearer manner. But computationally the classical description is not superior. There will be a definite advantage for more realistic electronic Hamiltonians, i.e., for implementing configuration interaction, and/or when the nuclear motion is coupled to the electronic dynamics. In this paper we limit attention to a derivation and discussion of the simple orbital approximation. (C) 2000 American Institute of Physics. [S0021-9606(00)30435-4].}, issn = {0021-9606}, doi = {10.1063/1.1288915}, author = {Remacle, F. and LEVINE, RD} } @article { ISI:000086025300025, title = {Configuration interaction between covalent and ionic states in the quantal and semiclassical limits with application to coherent and hopping charge migration}, journal = {JOURNAL OF PHYSICAL CHEMISTRY A}, volume = {104}, year = {2000}, month = {MAR 23}, pages = {2341-2350}, abstract = {Charge transport in molecular and extended systems is discussed with special reference to the mixing of covalent and ionic states and the evolution of this mixing with time. The formalism allows the electron to acquire an extra phase when it moves from one site to the next so that a hopping limit can be reached where the electron transfers with a random phase. The equations of motion are solved for both quantum mechanical and classical dynamics. An appendix discusses a classical representation of orbital occupancies in a manner consistent with the Pauli exclusion principle.}, issn = {1089-5639}, doi = {10.1021/jp992924i}, author = {Remacle, F. and LEVINE, RD} } @article { ISI:000165670900004, title = {Delayed ionization and fragmentation en route to thermionic emission: Statistics and dynamics}, journal = {ANNUAL REVIEW OF PHYSICAL CHEMISTRY}, volume = {51}, year = {2000}, pages = {65-98}, abstract = {Thermionic emission is discussed as a long time (microseconds) decay mode of energy-rich large molecules, metallic and metcar clusters, and fullerenes. We review what is known and consider the many experiments, systems, and theoretical and computational studies that still need to be done. We conclude with a wish list for future work. Particular attention is given to the experimental signatures, such as the dependence on the mode of energy acquisition, and theoretical indications of a not-quite-statistical delayed ionization and to the competition of electron emission with other decay modes, such as fragmentation or radiative cooling. Coupling of the electronic and nuclear modes can be a bottleneck and quite long time-delayed ionization can be observed, as in the decay of high Rydberg states probed by ZEKE spectroscopy, before the onset of complete energy partitioning.}, issn = {0066-426X}, doi = {10.1146/annurev.physchem.51.1.65}, author = {Campbell, EEB and LEVINE, RD} } @article { ISI:000086950500015, title = {Electronic response of assemblies of designer atoms: The metal-insulator transition and the role of disorder}, journal = {JOURNAL OF THE AMERICAN CHEMICAL SOCIETY}, volume = {122}, year = {2000}, month = {MAY 3}, pages = {4084-4091}, abstract = {Quantum dots present the chemist with the opportunity to synthesize atomic-like building blocks with made-to-measure electronic properties. For the theorists this allows a study of the same Hamiltonian for a range of parameters. Hen we consider a lattice of quantum dots, where the dots can be prepared with a narrow distribution of properties but are never quite identical. This is unlike an ordered lattice of atoms or molecules. We report computations of the frequency-dependent dielectric response of a two-dimensional array of quantum dots, as a function of the distance between the dots. When the dots are not closely packed, the response is dominated by the Coulomb repulsion of electrons (of opposite spin) on a given dot. This gives rise to an insulator-metal transition as the expanded array is compressed. The interplay between the three effects, the {\textquoteleft}{\textquoteleft}disorder{\textquoteright}{\textquoteright} due to the size, shape, and environmental fluctuations of the dots, the coupling of adjacent dots, and the Coulomb repulsion are studied as functions of the lattice spacing. The computations are performed in the approximation where each dot carries one valence electron, but these electrons are fully correlated so as to fully account for the Coulomb blocking. This is possible by a diagonalization of the Hamiltonian in a many-electron basis. Comparison is made with experimental results for the dielectric response, as described in a companion to this paper.}, issn = {0002-7863}, doi = {10.1021/ja9915448}, author = {Remacle, F. and LEVINE, RD} } @article { ISI:000085154400043, title = {K+CH3I -> KI+CH3 revisited: the total reaction cross section and its energy and orientation dependence. A case study of an intermolecular electron transfer}, journal = {PHYSICAL CHEMISTRY CHEMICAL PHYSICS}, volume = {2}, year = {2000}, pages = {757-767}, abstract = {The dynamics of the K + CH3I reaction is discussed with special reference to two factors that govern the electron transfer. One is that at higher collision velocity the behavior need not be adiabatic so that there can be a finite probability for the electron not to transfer, resulting in no reaction. The other is the marked increase of the electron affinity of CH3I with its bond extension. The electron transfer can therefore take place at much larger separation of the reactants if CH3I is stretched. The barrier to reaction is then much lower. These observations are used to discuss the stereodynamics of the reaction. Several open problems are identified.}, issn = {1463-9076}, doi = {10.1039/a907701d}, author = {Wiskerke, AE and Stolte, S and Loesch, HJ and LEVINE, RD} } @article { ISI:000165355400049, title = {Broken symmetry in the density of electronic states of an array of quantum dots as computed for scanning tunneling microscopy}, journal = {JOURNAL OF PHYSICAL CHEMISTRY A}, volume = {104}, year = {2000}, month = {NOV 16}, pages = {10435-10441}, abstract = {Broken symmetry is characteristic of arrays of quantum dots and can be observed in the failure of selection rules of optical spectroscopy or in the dielectric properties. Here we discuss scanning tunneling spectroscopy, where electrons are detached or attached. In the lowest order of description (sometimes known as Koopmans theorem), the orbitals of a system are regarded as given and, one adds or removes electrons from these orbitals. if one has a half-full band of states whose energies have a reflection symmetry about the center, the density of states should be symmetric about the energy of the highest occupied state. Features that are special to arrays of nanodots and lead to the breaking of the expected symmetry are identified. Computations of the density of states of an array of Ag nanodots that are in accord with the available experimental observations are also provided. For a disordered array, the response of the STM probe can be qualitatively different at different lattice points and we interpret this in terms of a change in the nature of the ground electronic state of the array when it is more disordered.}, issn = {1089-5639}, doi = {10.1021/jp0012956}, author = {Remacle, F. and LEVINE, RD} } @article { ISI:000083334200027, title = {Concluding remarks}, journal = {FARADAY DISCUSSIONS}, volume = {113}, year = {1999}, pages = {493-498}, issn = {0301-7249}, doi = {10.1039/a906167c}, author = {LEVINE, RD} } @article { ISI:000080583100006, title = {Architectonic quantum dot solids}, journal = {ACCOUNTS OF CHEMICAL RESEARCH}, volume = {32}, year = {1999}, month = {MAY}, pages = {415-423}, issn = {0001-4842}, doi = {10.1021/ar980039x}, author = {Markovich, G and Collier, CP and Henrichs, SE and Remacle, F. and LEVINE, RD and Heath, J. R.} } @article { ISI:000079012200012, title = {Charge migration and control of site selective reactivity: The role of covalent and ionic states}, journal = {JOURNAL OF CHEMICAL PHYSICS}, volume = {110}, year = {1999}, month = {MAR 15}, pages = {5089-5099}, abstract = {A many-electron description of charge migration along a molecular backbone is discussed. Reference is made to site selective reactivity and the recent experiments of Weinkauf and Schlag on the dissociation of peptide ions following a localized ionization. The use of many-electron states allows a classification of the charge migration pathways through either covalent or ionic states. Electron correlation is introduced via Coulomb repulsion of electrons of opposite spins a-la Hubbard. Complete configuration interaction is implemented using the unitary group basis of Paldus. The primary factor determining charge migration is found to be the local ionization potential. It is shown that, at lower levels of excitation, the majority of possible initial states which describe localized ionization at one end of the chain lead to a preferential dissociation at the other end of the chain. (C) 1999 American Institute of Physics. [S0021-9606(99)30111-2].}, issn = {0021-9606}, doi = {10.1063/1.478406}, author = {Remacle, F. and LEVINE, RD} } @article { ISI:000084318700018, title = {Driving high threshold chemical reactions by cluster-surface collisions: Molecular dynamics simulations for CH3I clusters}, journal = {JOURNAL OF PHYSICAL CHEMISTRY A}, volume = {103}, year = {1999}, month = {DEC 9}, pages = {10179-10186}, abstract = {Computational results for the surface impact of (CH3I)(n) clusters are presented, and the dynamics of formation of molecular products is examined. The mechanism is compared to the high energy bimolecular CH3I + CH3I collision and to other reactions in impact-heated clusters, in particular, the burning of air. The results are discussed in reference to the experimentally: observed formation of molecular iodine (as I-2(-)) in surface collisions of (CH3I)(n)(-) clusters.}, issn = {1089-5639}, doi = {10.1021/jp991823h}, author = {Kornweitz, H and Raz, T and LEVINE, RD} } @article { ISI:000084318700014, title = {Electronic control of site selective reactivity: A model combining charge migration and dissociation}, journal = {JOURNAL OF PHYSICAL CHEMISTRY A}, volume = {103}, year = {1999}, month = {DEC 9}, pages = {10149-10158}, abstract = {For large molecules, electronically excited stales are denser than can be simply judged from the gap between the ground state and excited states. This is particularly true for large open shell systems, such as peptide cations. In such systems, short laser pulses can be used to prepare initial electronic states that are not stationary. These are non Born-Oppenheimer states, and therefore, the motion of the nuclei is not determined by a single potential. It is argued that such states could offer the possibility of control of reactivity. They can impede the usually facile vibrational energy redistribution, which is characteristic for a motion on a potential surface with a well. After a localized ionization, the dependence of site-selective fragmentation of small peptide ions on time is discussed with computational results based on a Pariser-Parr-Pople Like electronic Hamiltonian. We predict a strong nonstatistical and site selective reactivity on a short time scale and also a dependence on the nature of the initial excitation. Results are presented for the fragmentation of Leu-Leu-Leu-Trp(+) and Ala-Ala-Ala-Tyr(+) ions and are compared with nanosecond laser pulse experiments.}, issn = {1089-5639}, doi = {10.1021/jp991853k}, author = {Remacle, F. and LEVINE, RD and Schlag, E. W. and Weinkauf, R.} } @article { ISI:000080144200014, title = {Electronically non-adiabatic transitions in high-energy CH3I+CH3I collisions computed by the quantal FMS method using the Evans-Polanyi potential}, journal = {CHEMICAL PHYSICS LETTERS}, volume = {304}, year = {1999}, month = {MAY 7}, pages = {385-392}, abstract = {The effective energy threshold for the crossing into an electronically excited state and the post threshold rise of the yield of crossing are discussed. The time-dependent Schrodinger equation for multiple electronic states is solved using the full multiple spawning (FMS) methodology. The quantal results are compared with classical path methods. The potential energy function is of the LEP form including the electronically excited surface. For kinematic reasons, the yield is exponentially small until an effective threshold, at similar to 10 km s(-1), with a steep rise of the yield in the post threshold regime. (C) 1999 Elsevier Science B.V. All rights reserved.}, issn = {0009-2614}, doi = {10.1016/S0009-2614(99)00337-1}, author = {Chajia, M and LEVINE, RD} } @article { ISI:000082080400003, title = {On the independence of correlated events}, journal = {INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY}, volume = {74}, year = {1999}, month = {SEP 15}, pages = {467-478}, abstract = {Why do some quite complex events appear to be built up from seemingly independent elementary events? It is, of course, fortunate that this is so, for otherwise, it would be hard to analyze the world around us. But the technical question remains. It is here argued that a sufficient condition is that the possible complex events all have the same sum(s) for (one or more) additive variable(s). Constants of the motion are one example of such variables. In addition, it is shown that the independent distribution of the elementary events is one of maximal entropy. (C) 1999 John Wiley \& Sons, Inc.}, issn = {0020-7608}, author = {LEVINE, RD} } @article { ISI:000079508300034, title = {Reactive and nonreactive charge transfer by the FMS method: low energy H++D-2, and H+H-2(+) collisions}, journal = {PHYSICAL CHEMISTRY CHEMICAL PHYSICS}, volume = {1}, year = {1999}, month = {MAR 15}, pages = {1205-1212}, abstract = {The full multiple spawning (FMS) methodology for solving the time dependent Schrodinger equation for multiple electronic states is extended to reactive collisions on several electronic states. The computational complexity remains unchanged, less than double that of a quasiclassical trajectory computation. It is shown how the spawning approach can describe the bifurcation of the wave function into components exiting in different directions of space, as is the case when rearrangement of the atoms takes place. Low energy H+ + D-2 and H + H-2 + collisions, which result in both reactive and nonreactive charge transfer are used as an illustration. The FMS method is used to generate converged opacity functions and cross sections even at higher energies when dissociation is energetically allowed. This suggests that also on a single potential energy function the FMS method offers a viable route to full dimensional reactive quantal scattering computations. For the H-3(+) system, a diatomics in molecules (DIM) potential energy function is used in a diabatic basis where three electronic states are coupled. Comparison is made with the classical path approximation, the trajectory surface hopping method and stationary quantum mechanical scattering computations, which used the sudden approximation and the coupled states method. For the H+ + D-2 collision, our results are close to those already published. The computations for the H + H-2(+) collision, where the initial channel is an excited one, are distinctly different from the results of earlier, approximate, approaches.}, issn = {1463-9076}, doi = {10.1039/a807824f}, author = {Chajia, M and LEVINE, RD} } @article { ISI:000072889100006, title = {Charge directed reactivity: a simple electronic model, exhibiting site selectivity, for the dissociation of ions}, journal = {CHEMICAL PHYSICS LETTERS}, volume = {285}, year = {1998}, month = {MAR 13}, pages = {25-33}, abstract = {A Huckel-type effective Hamiltonian is used to examine the conditions for site-selected reactivity. The example is the dissociation of a positive ion, as in mass spectrometry. Coupling to the dissociative channels is included by a rate operator. We examine the time evolution of the charge and bond order matrices and of the yield of fragments following a localized initial ionization. Dissociation is found to follow the (positive) charge. Variations in the local properties can markedly change the dissociation pattern. A more statistical limit is reached when the migration of charge is unimpeded. (C) 1998 Elsevier Science B.V.}, issn = {0009-2614}, doi = {10.1016/S0009-2614(97)01314-6}, author = {Remacle, F. and LEVINE, RD and M.A. Ratner} } @article { ISI:000073231200023, title = {Electronically non-adiabatic transitions in the Evans-Polanyi valence bond model}, journal = {CHEMICAL PHYSICS LETTERS}, volume = {286}, year = {1998}, month = {APR 3}, pages = {155-162}, abstract = {Translational to electronic energy transfer with or without a concomitant chemical reaction is studied for the Evans-Polanyi model. We explore the possibility of light emission from an electronically excited stare following a high-energy collision. This can be viewed as an inverse process to a Woodward-Hoffmann photochemically allowed four-center reaction. The collision is described using this Evans-Polanyi method where the two diabatic electronic states correlate with the states of the reactants and products. The effective coupling of the diabatic starts is found to be localized and the non-adiabatic regime is transversed rapidly so that facile electronic excitation is possible. (C) 1998 Elsevier Science B.V.}, issn = {0009-2614}, doi = {10.1016/S0009-2614(97)01459-0}, author = {Dobrovsky, I and LEVINE, RD} } @article { ISI:000071765300003, title = {On the inverse Born-Oppenheimer separation for high Rydberg states of molecules}, journal = {INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY}, volume = {67}, year = {1998}, month = {MAR 15}, pages = {85-100}, abstract = {The separation of radial electronic and nuclear motions is discussed with special reference to high Rydberg states of molecules. An inverse separation is obtained when the rapid nuclear motion instantaneously adjusts itself to the position of the Rydberg electron. The electron moves in the potential averaged over the position of the nuclei (and their valence electrons). This inverse separation is useful when omega n(3) > 1, where omega is the spacing of nuclear energy states (in au) and n is the principal quantum number of the Rydberg electron whose orbital period increases as n(3). The inverse Born-Oppenheimer separation can break down owing to the finite kinetic energy of the Rydberg electron. Like the Born-Oppenheimer separation, its inverse can also be formulated in an adiabatic or a diabatic basis. The diabatic inverse Born-Oppenheimer is practical both for interpretation of zero electron kinetic energy (ZEKE) spectra and for computations. Explicit results are given for a model system of an electron orbiting a vibrating dipole, identifying the relevant coupling constants. The discussion emphasizes the radial motion and the limits discussed here are not quite equivalent to the four (or, actually, five) Hund{\textquoteright}s coupling cases relevant to angular momentum coupling schemes. (C) 1998 John Wiley \& Sons, Inc.}, issn = {0020-7608}, doi = {10.1002/(SICI)1097-461X(1998)67:2<85::AID-QUA3>3.3.CO;2-K}, author = {Remacle, F. and LEVINE, RD} } @article { ISI:000073473500021, title = {Monte Carlo, maximum entropy and importance sampling}, journal = {CHEMICAL PHYSICS}, volume = {228}, year = {1998}, month = {MAR 1}, pages = {255-264}, abstract = {The probability of an error in a Monte Carlo integration is shown to be exponentially small in the number of points used, with the magnitude of the exponent being determined by a relevant entropy. Implications for importance sampling and for the significance of the maximum entropy formalism an discussed. Specifically it is shown that the optimal sampling distribution is one of maximal entropy. The Monte Cal-lo method or its variants play an essential role in classical trajectory computations. Practitioners are aware that generating few trajectories is already sufficient for typical quantities such as the mean energy of the products to settle down to the correct value. The present results provide further insight and suggest why a distribution of maximal entropy can provide such useful representation of the results. The discussion is based on the information theoretic bound for the error of transmission and can also be derived from the Chernoff bound in hypothesis testing. (C) 1998 Elsevier Science B.V.}, issn = {0301-0104}, doi = {10.1016/S0301-0104(97)00334-0}, author = {LEVINE, RD} } @article { ISI:000073303600004, title = {The transition from recoil to shattering in cluster-surface impact: An experimental and computational study}, journal = {INTERNATIONAL JOURNAL OF MASS SPECTROMETRY}, volume = {174}, year = {1998}, month = {MAR}, pages = {35-52}, abstract = {{{Size and kinetic energy distributions of the products of size and energy selected ammonia clusters, (NH3)(n)NH4+}, issn = {1387-3806}, doi = {10.1016/S0168-1176(97)00288-7}, author = {Christen, W and Even, U and Raz, T and LEVINE, RD} } @article { ISI:000075256200033, title = {Collisional energy loss in cluster surface impact: Experimental, model, and simulation studies of some relevant factors}, journal = {JOURNAL OF CHEMICAL PHYSICS}, volume = {108}, year = {1998}, month = {JUN 22}, pages = {10262-10273}, abstract = {{{Measurements of the collisional energy transfer of size and energy-selected ammonia cluster ions (NH3)(n)H+}, issn = {0021-9606}, doi = {10.1063/1.476487}, author = {Christen, W and Even, U and Raz, T and LEVINE, RD} } @article { ISI:000074278600020, title = {The exoergic F+CH4 reaction as an example of peripheral dynamics}, journal = {CHEMICAL PHYSICS LETTERS}, volume = {289}, year = {1998}, month = {JUN 5}, pages = {125-131}, abstract = {Classical trajectory computations for thermal reactants on a six-atom potential show a forward scattering component which is correlated with the HF product being formed with high vibrational excitation. These trajectories are peripheral collisions where the F atom approaches CH4 with a high impact parameter and reaction is through a nearly collinear F-H-C configuration with a stretched F-H bond. Other trajectories are well described by a hard-sphere model whose cutoff is below the range of peripheral collisions. Comparison is made with the F + H(2 )and other reactions where nearly thermoneutral channels correlate with forward scattering. (C) 1998 Elsevier Science B.V. All rights reserved.}, issn = {0009-2614}, doi = {10.1016/S0009-2614(98)00387-X}, author = {Kornweitz, H and Persky, A and LEVINE, RD} } @article { ISI:000075864200022, title = {Formation of molecular iodine in high-energy four-center CH3I+CH3I collisions}, journal = {CHEMICAL PHYSICS LETTERS}, volume = {294}, year = {1998}, month = {SEP 11}, pages = {153-161}, abstract = {Classical trajectory computations and a kinematic analysis of the collision of two CH3I molecules are presented. The yield of molecular and atomic iodine is examined as a function of reactant translational and vibrational energy. The potential energy function is of the LEP form, which has a high late barrier where all bonds are extended. Vibrational excitation of CH3I enhances the barrier crossing and molecular products are formed highly vibrationally excited. Kinematic considerations indicate the same trends. The results are discussed as a possible mechanism for the formation of molecular iodine via ultrafast heating achieved in wall collisions of CH3I clusters. (C) 1998 Elsevier Science B.V. All rights reserved.}, issn = {0009-2614}, doi = {10.1016/S0009-2614(98)00849-5}, author = {Kornweitz, H and LEVINE, RD} } @article { ISI:000076380800008, title = {Networks of quantum nanodots: The role of disorder in modifying electronic and optical properties}, journal = {JOURNAL OF PHYSICAL CHEMISTRY B}, volume = {102}, year = {1998}, month = {OCT 1}, pages = {7727-7734}, abstract = {Disorder is shown to induce qualitative changes in the electronic spectrum and hence in the response of assemblies of quantum dots. Lattices of quantum dots have one unique source of disorder: the dots themselves can be prepared with a narrow distribution of properties but they are never quite identical. This is unlike a lattice of atoms or molecules. In addition, lattices of quantum dots have a configurational disorder and can also be prepared with compositional disorder. The relaxation of selection rules and the splittings of degeneracies due to symmetry breaking induced by these fluctuations can be probed by optical means. Special attention is given to the enhancement and to the variation of the second harmonic response as a function of the spacing between the dots.}, issn = {1089-5647}, doi = {10.1021/jp9813948}, author = {Remacle, F. and Collier, CP and Markovich, G and Heath, J. R. and Banin, U and LEVINE, RD} } @article { ISI:000077543700001, title = {Prompt and delayed dissociation of energy-rich larger molecules}, journal = {JOURNAL OF PHYSICAL CHEMISTRY A}, volume = {102}, year = {1998}, month = {DEC 10}, pages = {10195-10198}, abstract = {Coexistence of prompt and delayed decay modes of energized polyatomic molecules is discussed with reference to the special features of larger molecules which makes it amenable to experimental observation by a suitable choice of initial conditions. The molecular parameters identified by the RRKM theory of unimolecular (delayed) decay suffice to characterize the prompt process as well. The expected {\textquoteleft}{\textquoteleft}kinetic stability{\textquoteright}{\textquoteright} of large molecules is thus not necessarily the rule, and fast processes are possible, suggesting the possibility of experimental control.}, issn = {1089-5639}, doi = {10.1021/jp981912e}, author = {Remacle, F. and LEVINE, RD} } @article { ISI:000075052000030, title = {The transition from localized to collective electronic states in a silver quantum dots monolayer examined by nonlinear optical response}, journal = {CHEMICAL PHYSICS LETTERS}, volume = {291}, year = {1998}, month = {JUL 17}, pages = {453-458}, abstract = {The optical second-harmonic response of a finite hexagonal lattice is computed as a function of the inter particle separation. In agreement with experiments on Langmuir monolayers of silver quantum dots, the computed response exhibits a peak due to a transition from localized electronic states to a band-like structure. The localization is due to the fluctuations in the particle size and position. For a perfect lattice the variation of the nonlinear response with the inter particle separation is qualitatively different. The role of the symmetry breaking is demonstrated at the tight binding level of electronic structure computations. (C) 1998 Elsevier Science B.V. All rights reserved.}, issn = {0009-2614}, doi = {10.1016/S0009-2614(98)00612-5}, author = {Remacle, F. and Collier, CP and Heath, J. R. and LEVINE, RD} } @article { ISI:000075990100005, title = {Two classes of ZEKE spectroscopy}, journal = {COLLECTION OF CZECHOSLOVAK CHEMICAL COMMUNICATIONS}, volume = {63}, year = {1998}, month = {AUG}, pages = {1143-1151}, abstract = {A classification of ZEKE spectra into two classes based on operational criteria is useful for discussion. The proposal is that some of the different and seemingly conflicting effects reported for different molecular (or the same molecule for different excitations), such as the role of an external field, are due to these two distinct classes of states which can be optically accessed. Class A is the direct, {\textquoteleft}{\textquoteleft}front door{\textquoteright}{\textquoteright} entry where the states excited are those which are detected by the delayed ionization. Class B is a very prevalent but indirect {\textquoteleft}{\textquoteleft}backdoor{\textquoteright}{\textquoteright} route where it is only the interaction of the Rydberg electron with the core, possibly aided by external perturbations, that allows a signal to be detected upon ionization. The operational criteria for distinguishing between or even exploiting the features of the two classes are discussed. Such attention might be useful as new techniques for class B spectra are developed.}, issn = {0010-0765}, doi = {10.1135/cccc19981143}, author = {Selzle, H. L. and Schlag, E. W. and Remacle, F. and LEVINE, RD} } @article { ISI:A1997WL50100011, title = {Molecular reaction dynamics looks toward the next century: Understanding complex systems}, journal = {PURE AND APPLIED CHEMISTRY}, volume = {69}, year = {1997}, note = {35th IUPAC Congress, ISTANBUL, TURKEY, AUG 14-19, 1995}, month = {JAN}, pages = {83-90}, publisher = {IUPAC}, abstract = {Chemical reaction dynamics is making increasing contact with {\textquoteleft}real{\textquoteright} chemistry: examination of more elaborate reaction mechanisms typical of organic chemistry, the study of chemical reactions where the medium plays an active role (as is often the case in solution and on surfaces) and the ability to mimic systems of biochemical complexity are all of current interest. Much of our early conceptual understanding was acquired by the study of isolated, simple chemical exchange reactions in which one bond is broken and another bond is formed, in concert. A central feature in these reactions is the high selectivity which can be achieved by the choice of initial conditions and the considerable specificity of the resulting products. These themes do carry over to the world of more complex systems. Applications discussed include four center reactions, activated chemical reactions in solution, in clusters and on surfaces and photochemical processes. Surprisal analysis, long used to characterize the selectivity and specificity in simple reactions, is equally applicable here and the dynamical origin for the approach is discussed. The primary conclusion is that at the dawn of the new millennium, chemical reaction dynamics is ready to make inroads into the world of reactions of realistic complexity.}, issn = {0033-4545}, doi = {10.1351/pac199769010083}, author = {LEVINE, RD} } @article { ISI:000072547500013, title = {Dynamic bottlenecks and the extreme stability of high Rydberg states}, journal = {ACH-MODELS IN CHEMISTRY}, volume = {134}, year = {1997}, pages = {619-634}, abstract = {High molecular Rydberg states, whose time evolution exhibits multiple time scales are discussed as an example of a system which can be examined in detail. Three bottlenecks to the sampling of phase space, associated with an incomplete mixing of the zeroth order quantum numbers, are identified. The physics of all three is that the number of open ionization channels is smaller than the number of quasi isoenergetic zero order discrete states and that an electron with a high orbital angular momentum, which is far from the core, cannot effectively couple to it. States trapped behind the bottlenecks have a high resilience to decay and such states are possible even high above the ionization threshold and in the presence of external perturbations. On the other hand, states that are directly coupled to the ionization channels decay promptly, with less sampling of the dense manifold of isoenergetic delayed states. We conclude that the decay of high molecular Rydberg states provides a useful analogue for unimolecular reactions from a dense set of states which typically results in a prompt and a delayed decay.}, issn = {1217-8969}, author = {Remacle, F. and LEVINE, RD} } @article { ISI:A1997XA80400012, title = {Multiple traversals of a conical intersection: electronic quenching in Na*+H-2}, journal = {CHEMICAL PHYSICS LETTERS}, volume = {270}, year = {1997}, month = {MAY 23}, pages = {319-326}, abstract = {The conical intersection in the collision of a Na(3p(2)P) atom with H-2, occurs at large H-H distances, Time dependent quantal computations exhibit many sequential non-adiabatic couplings, each of which is localized in time, where the quenching probability per traversal is small. During the collision, the population of the ground state increases almost in a random walk fashion until the partners recede after many H-2, vibrational periods. Changing the masses suggests that other systems can also exhibit such a snarled quenching process which cannot be described as a single non-adiabatic event per collision.}, issn = {0009-2614}, doi = {10.1016/S0009-2614(97)00369-2}, author = {BENNUN, M and Martinez, TJ and LEVINE, RD} } @article { ISI:A1997WP01200034, title = {Non-adiabatic molecular dynamics: Split-operator multiple spawning with applications to photodissociation}, journal = {JOURNAL OF THE CHEMICAL SOCIETY-FARADAY TRANSACTIONS}, volume = {93}, year = {1997}, month = {MAR 7}, pages = {941-947}, abstract = {A classically motivated quantal method, designed to allow for molecular dynamics occurring on more than one potential-energy surface, is extended in two directions. The extensions are shown to be accurate while retaining the classical flavour which is useful for both interpretation and computation. The first extension allows for the evaluation of the required inter-state coupling matrix elements for potential-energy surfaces even when these are given numerically rather than fitted to some analytical form. Moreover, the procedure is a local one, requiring only the values of the two potentials and their gradients. It is thus particularly suitable for applications where the electronic and nuclear problems are solved simultaneously. The second extension strengthens the connections to classical mechanics while avoiding ambiguities in the choice of the classical trajectories which will represent the dynamics. The accuracy and limitations of the proposed procedures are tested for several model problems.}, issn = {0956-5000}, doi = {10.1039/a605958i}, author = {Martinez, TJ and LEVINE, RD} } @article { ISI:A1997XU11500005, title = {Physical aspects and quantitative theory of time resolved spectroscopy of high molecular Rydberg states}, journal = {JOURNAL OF CHEMICAL PHYSICS}, volume = {107}, year = {1997}, month = {SEP 1}, pages = {3382-3391}, abstract = {The qualitative physical aspects and the quantitative description of time and frequency resolved absorption spectroscopy of high molecular Rydberg states are discussed. The frequency is that of the excitation laser and the time is the independently variable delay before detection. The discussion allows for the presence of a weak external electrical field. The essential new ingredient is the finite slice of Rydberg states that are detected (=are in the detection window) and the variation of this population with time due to the coupling of the Rydberg electron with the molecular core. Line shapes are provided showing the effect of the depth of the detection window and the advantages and limitations imposed by the finite width of the excitation laser. The sharpening of the spectrum as the delay time to detection is increased is also illustrated. The quantitative theory is expressed in terms of the expectation value of a detection operator; describing the range of states that can be ionized by the delayed field, taken over a wave function. This wave function is the state of the system at the time of detection. However, even just at the end of the excitation stage, due to the interseries coupling, this wave function is not identical to the state that is directly optically accessed. The time correlation function of this wave function, obtained as a Fourier transform. of the frequency resolved spectrum, is shown to provide further insight into the dynamics, the more so when the excitation laser has a narrow width in frequency. (C) 1997 American Institute of Physics.}, issn = {0021-9606}, doi = {10.1063/1.475142}, author = {Remacle, F. and LEVINE, RD} } @conference { ISI:A1997BJ51W00023, title = {Separation of time scales in the dynamics of high molecular Rydberg states}, booktitle = {CHEMICAL REACTIONS AND THEIR CONTROL ON THE FEMTOSECOND TIME SCALE XXTH SOLVAY CONFERENCE ON CHEMISTRY}, series = {Advances in Chemical Physics}, volume = {101}, year = {1997}, note = {XXth Solvay Conference on Chemistry, FREE UNIV BRUSSELS, BRUSSELS, BELGIUM, NOV 28-DEC 02, 1995}, pages = {625-646}, isbn = {0-471-18048-3}, issn = {0065-2385}, doi = {10.1002/9780470141601.ch23}, author = {LEVINE, RD}, editor = {Gaspard, P and Burghardt, I} } @article { ISI:A1997XU11500006, title = {Time and frequency resolved spectra of high molecular Rydberg states by dynamical computations}, journal = {JOURNAL OF CHEMICAL PHYSICS}, volume = {107}, year = {1997}, month = {SEP 1}, pages = {3392-3401}, abstract = {The absorption spectrum of bound Rydberg states which can be detected by a delayed, pulsed field ionization is computed. The spectrum, measured for various delay times, provides information on the short and the longer time dynamics of high molecular Rydberg states. A quantitative dynamical theory, based on an effective Hamiltonian formalism is applied, illustrating the role of the Rydberg electron-core coupling and of an external electrical field in the delay-time dependent spectra. The sharpening of the spectra for longer delay times is reproduced by the dynamical computations. It is found that the overall intensity, as a function of the delay time before detection, is well described by a double exponential decay where the short lifetime is primarily a manifestation of the direct autoionization to the continuum, while the long lifetime is due to interseries coupling. Both lifetimes increase with the principal quantum number of the Rydberg states. The notion of trapped {\textquoteleft}{\textquoteright}reservoir states{\textquoteright}{\textquoteright} is illustrated by the computational results, with special reference to a kinetic model analysis. The role of the initially optically accessed state(s) and of the depth of detection, in particular with regard to the intensity, is demonstrated. The effect of varying the strength of an external de field in the time interval prior to the detection is illustrated by the dynamical computations, with respect to both the decay kinetics and the intensity of the spectrum. (C) 1997 American Institute of Physics.}, issn = {0021-9606}, doi = {10.1063/1.474713}, author = {Remacle, F. and LEVINE, RD} } @article { ISI:000072547500011, title = {A time dependent view of the statistics of spectral intensities - Comment}, journal = {ACH-MODELS IN CHEMISTRY}, volume = {134}, year = {1997}, pages = {613-617}, issn = {1217-8969}, author = {Remacle, F. and LEVINE, RD} } @article { ISI:A1997YA48400010, title = {Dynamical stereochemistry on several electronic states: A computational study of Na*+H-2}, journal = {JOURNAL OF PHYSICAL CHEMISTRY A}, volume = {101}, year = {1997}, month = {OCT 9}, pages = {7522-7529}, abstract = {The orbital control of stereochemistry is discussed with special reference to the Na (3p P-2) + H-2 collision. As seen by H-2, the p orbital of the electronically excited Na atom is like a quadrupole, which may or may not lock along the molecular axis. Quantum mechanically, variations in the alignment of the orbital represent changes in the electronic state of the system and so dynamical methods which allow for such interstate transitions must be used. A new, time dependent quantum mechanical method for propagating the wave function on several electronic states is used to study these interstate transitions. Particular attention is given to the question of orbital following. The computational method is fully quantum mechanical but it uses a basis set which takes full account of the classical motion on any given electronic state while the solution of the Schrodinger equation addresses the electronic-state-changing transitions. We pay specific attention to the orbital alignment for both cold and rotationally warm H-2 and for low and high impact parameters throughout the course of the collision. It is concluded that orbital locking is not necessarily instantaneous and can lag behind the faster nuclear motion, including the (fast) rotational motion of H-2.}, issn = {1089-5639}, doi = {10.1021/jp971058b}, author = {BENNUN, M and Martinez, TJ and LEVINE, RD} } @article { ISI:A1997YE04100017, title = {{\textquoteleft}{\textquoteright}Forbidden{\textquoteright}{\textquoteright} four-center reactions: Molecular orbital considerations for N-2+N-2 and N-2+N-2(+)}, journal = {JOURNAL OF PHYSICAL CHEMISTRY A}, volume = {101}, year = {1997}, month = {OCT 30}, pages = {8255-8263}, abstract = {The hypothetical four-center nitrogen exchange reaction of N-2 + N-2 is analyzed. We show that the three level crossings accompanying the least-motion nitrogen exchange reaction occur at different points along the reaction coordinate, leading to a mechanism requiring three {\textquoteleft}{\textquoteright}singly forbidden{\textquoteright}{\textquoteright} reaction steps. Simple MO arguments show that the loss of one electron in N-2 + N-2(+) reduces the energy demand associated with the energetically dominating first and third level crossing,, suggesting that ionization of the reaction system lowers significantly the high activation barrier. This is supported by nonlocal density functional calculations on various N-4 and N-4(+) structures, which, however, also indicate that the barrier still remains at high energy: the tetraazacyclobutadiene intermediate involved in the neutral reaction is 166.7 kcal/mol higher in energy than N-2 + N-2; the corresponding radical cation is only 52.2 kcal/mol above N-2 + N-2(+). The DFT results also indicate that the N-2 + N-2(+) nitrogen exchange reaction, if it occurs at all, may also proceed via a competing mechanism involving a T-shaped transition state at 102.8 kcal/mol above N-2 + N-2(+). Suggestions for further experimental investigations emerge from this analysis.}, issn = {1089-5639}, doi = {10.1021/jp971005u}, author = {Bickelhaupt, FM and Hoffmann, R and LEVINE, RD} } @article { ISI:A1997XV73400006, title = {Molecular collision dynamics on several electronic states}, journal = {JOURNAL OF PHYSICAL CHEMISTRY A}, volume = {101}, year = {1997}, month = {SEP 4}, pages = {6389-6402}, abstract = {A time-dependent quantum mechanical method for propagating the wave function on several electronic states is discussed for the polyatomic case and illustrated by the quenching collision of a Na (3p P-2) atom by H-2. The specification of method is governed by the need to have a clear physical interpretation of the results, by the recognition that the motion on a given electronic state can often (but not always) be well approximated by classical mechanics, and by the need for a computational procedure that is simple enough to handle polyatomic systems. These desiderata are realized by the spawning technique which is discussed in detail. One more feature of the method is that it allows for a smooth interface with the methodologies of quantum chemistry so that the electronic structure problem can be solved simultaneously with the time propagation of the nuclear dynamics. The method is derived from a variational principle and so can yield quantum mechanically numerically converged results. The parameters that govern the numerical accuracy of the method are explicitly discussed with special reference to their physical significance. The quenching of a Na (3p P-2) atom by H-2 due to a conical intersection of two potential energy surfaces is used as a computational example since it illustrates many of the features of the method. This collision is found to be sticky and exhibits many sequential nonadiabatic couplings, each of which is localized in time, where the quenching probability per traversal of the conical intersection region is small. However, the accumulated transfer of population to the ground state can be significant since the duration of the overall transfer is spread over many vibrational periods of H-2.}, issn = {1089-5639}, doi = {10.1021/jp970842t}, author = {Martinez, TJ and BENNUN, M and LEVINE, RD} } @article { ISI:A1997YB79500004, title = {Nonstationary electronic states and site-selective reactivity}, journal = {JOURNAL OF PHYSICAL CHEMISTRY A}, volume = {101}, year = {1997}, month = {OCT 16}, pages = {7702-7710}, abstract = {An efficient route to the site-selective reactivity of electronically excited states of multicentered molecules is discussed. In the first stage the migration of the electronic excitation occurs. This can operate over an extensive range without extensive draining of energy into the nuclear frame. Only in a second stage, once the optimal site has been reached, does the excess energy become available for bond breaking or isomerization at the new, optimal, site. This two-stage mechanism, where electronic excitation (or the charge) is the scout, avoids the pitfall of conventional large molecule kinetics. (In that view, known as the quasi equilibrium theory, the electronic excitation is first converted to nuclear modes. But then there are so many available vibrational states that the probability for the excitation energy to become localized at the necessary site, is too small and the resulting reaction rate is too slow.) By confining the site search to the electronic manifold, it becomes a highly efficient process. The recent novel experiments of Weinkauf et al. on (positive) charge migration and dissociation of peptide ions are suggested as an example of the considerations above where there is a facile migration of the positive charge followed by reactivity at the selected site. The peptide is modeled as beads on a chain. Interbead and intrabead coupling are discussed in terms of adiabatic and diabatic states. We find a multistep mechanism (unlike superexchange): a charge-directed reactivity (CDR) model. Such efficient ranging could also take place in other chain structures and suggests that there will be examples where electronic processes set the time scale for the chemical change.}, issn = {1089-5639}, doi = {10.1021/jp9715742}, author = {Weinkauf, R. and Schlag, E. W. and Martinez, TJ and LEVINE, RD} } @article { ISI:A1996UY12200017, title = {Intramolecular dynamics in a congested set of states: A reduced description of the quantal long time evolution with application to high Rydberg states}, journal = {CHEMICAL PHYSICS LETTERS}, volume = {257}, year = {1996}, month = {JUL 19}, pages = {111-118}, abstract = {Time evolution when many states are strongly coupled is approximated by a reduced description where nearly degenerate states are taken to be equally populated, on the average. This grouping, valid at longer times, can significantly reduce the dimension of the problem, thereby making tractable computations which include all nearly isoenergetic states. The validity of the approach is examined by comparison with exact results, The application illustrated is to high molecular Rydberg states where a large basis size is required for convergence because, at times of experimental interest for ZEKE spectroscopy, many zero-order states have been accessed.}, issn = {0009-2614}, doi = {10.1016/0009-2614(96)00512-X}, author = {Remacle, F. and LEVINE, RD} } @article { ISI:A1996UB87800013, title = {On the quantum mechanical theory of unimolecular reactions through a narrow bottleneck: The prompt and delayed dissociation}, journal = {MOLECULAR PHYSICS}, volume = {87}, year = {1996}, month = {MAR}, pages = {899-917}, abstract = {The quantum dynamics of unimolecular dissociation are discussed for a typical situation where the number of energy rich but bound (zero order) states far exceeds the number of states with enough energy along the reaction coordinate in order to dissociate. It is shown that one can introduce a new basis of states, the {\textquoteleft}trapping{\textquoteright} states, which diagonalize the effective Hamiltonian that governs the dynamics in the bound subspace. The properties of these states are discussed with special reference to the two distinct time regimes (prompt and delayed) for the dissociation that are expected for such a congested level structure.}, issn = {0026-8976}, doi = {10.1080/00268979650027243}, author = {Remacle, F. and LEVINE, RD} } @article { ISI:A1996VZ91200001, title = {Time and frequency resolved ZEKE spectroscopy}, journal = {JOURNAL OF PHYSICAL CHEMISTRY}, volume = {100}, year = {1996}, month = {DEC 19}, pages = {19735-19739}, abstract = {ZEKE spectroscopy is based on delayed detection by pulsed field ionization. It is thereby possible to monitor the time evolution at a given excitation frequency. Moreover, by varying the depth of detection, one can harvest different Rydberg series. The qualitative features expected for such a spectrum are discussed. The quantitative theory required to compute spectra is outlined and applied to the realistic example of Na-2(+). The computed spectrum is found to very accurately exhibit two time scales, just as has been observed, with the shorter decay time being faster for lower Rydberg states. Extensive interseries coupling is noted.}, issn = {0022-3654}, doi = {10.1021/jp963005k}, author = {Remacle, F. and Even, U and LEVINE, RD} } @article { ISI:A1996UW83600008, title = {On the effects of an internal barrier on fast four-atom ion-molecule reactions}, journal = {JOURNAL OF CHEMICAL PHYSICS}, volume = {105}, year = {1996}, month = {JUL 15}, pages = {953-964}, abstract = {We investigate the influence of an internal barrier on an exothermic adiabatic reaction model between diatomic ions and molecules. Reaction cross-sections are calculated from quasi-classical trajectories for different initial vibrational and rotational states of the reactants and for relative collision energies in the range from 0.01 to 3 eV. It is shown that the height of a late internal barrier strongly influences both the characteristics of the state-selected cross-sections and the energy distributions of the products. In contrast to complex formation in the entrance region according to the Langevin model our analysis emphasizes the role of the full potential energy surface for an understanding of the dynamics of ion-molecule reactions. (C) 1996 American Institute of Physics.}, issn = {0021-9606}, doi = {10.1063/1.472815}, author = {Dubernet, ML and Rebentrost, F. and KOMPA, KL and LEVINE, RD} } @article { ISI:A1996VH46300005, title = {Electric field effects on long living ZEKE states}, journal = {JOURNAL OF PHYSICAL CHEMISTRY}, volume = {100}, year = {1996}, month = {SEP 19}, pages = {15320-15327}, abstract = {The effect of an electric field on the overall intensity of the ZEKE spectrum and on the lifetime is discussed for very long living states detected by a pulsed field ionization delayed by several microseconds or more. It is shown that the presence of a de electrical field can shorten the very long lifetimes and that it can also reduce the overall intensity of the very long living states, The decrease in the long lifetimes of the ZEKE states is complementary to the field-induced elongation of the shorter lifetimes. The discussion is based on quantum mechanical considerations and is illustrated by detailed computational studies, for a model problem, using an effective Hamiltonian formalism for an energy range just above the lowest ionization threshold, The model allows for coupling of different Rydberg series built on different excited states of the core where the continuum corresponds to the ground state. Predissociation is not allowed for in the model Hamiltonian. The trends are in accord with the observations of Held et al, as reported in the preceding paper, and the magnitude of the measured lifetimes of the ZEKE states (dozens of microseconds) are reproduced by the computations.}, issn = {0022-3654}, doi = {10.1021/jp9603804}, author = {Remacle, F. and LEVINE, RD and Schlag, E. W. and Selzle, H. L. and Held, A} } @article { ISI:A1996UZ04900008, title = {Cluster-surface impact dissociation of halogen molecules in large inert gas clusters}, journal = {CHEMICAL PHYSICS LETTERS}, volume = {257}, year = {1996}, month = {JUL 26}, pages = {273-279}, abstract = {Molecular dynamics simulations of the dissociation of I-2 embedded in large Ar-n (n = 319, 553) clusters, which impact at high velocities (upsilon = 7-15 km s(-1)) on Pt surfaces, result in information on heterogeneous and homogeneous dissociation mechanisms. A broad distribution of dissociation lifetimes is exhibited, which can be attributed to prompt and retarded heterogeneous dissociation and to prompt, retarded and outbound homogeneous dissociation events. The propagation of a microshock wave within a large cluster can be interrogated by the homogeneous dissociation of a chemical probe, with the velocity of the propagation of the dissociation front being close to the cluster impact velocity.}, issn = {0009-2614}, doi = {10.1016/0009-2614(96)00551-9}, author = {Schek, I and Jortner, J. and Raz, T and LEVINE, RD} } @article { ISI:A1996WB08400023, title = {Fast translational thermalization of extreme disequilibrium induced by cluster impact}, journal = {CHEMICAL PHYSICS}, volume = {213}, year = {1996}, month = {DEC 15}, pages = {263-275}, abstract = {Impact heating of cold molecular clusters moving at high velocities dissipates extreme amounts of energy (often more than several eV per atom) in very short times. Molecular dynamics simulations of larger rare gas clusters show that this excess energy is thermalized in 100 fs or less, depending on cluster size and impact velocity. Dissipation is also extensive for smaller clusters but these shatter before being fully thermalized. A simple analytical hard sphere model that recovers this behavior is discussed. The model attributes the ultrafast relaxation to the random orientation of the interatomic distance before the collision, A perfectly ordered army of atoms is indeed found not to relax. Such an array also allows for a dispersion-free propagation of a shock front. The route to equilibrium is therefore the efficient mixing in phase space caused by the velocity components after the collision having a random part. The implications for the maximum entropy description of cluster impact induced chemistry, for the production of electronically excited and ionic species and for electron emission are discussed.}, issn = {0301-0104}, doi = {10.1016/S0301-0104(96)00284-4}, author = {Raz, T and LEVINE, RD} } @article { ISI:A1996VG93200024, title = {Rotational autoionization and interseries coupling of high Rydberg states by the anisotropy of the molecular core: The quantal long time evolution}, journal = {JOURNAL OF CHEMICAL PHYSICS}, volume = {105}, year = {1996}, month = {SEP 15}, pages = {4649-4663}, abstract = {Using exact matrix elements for the coupling, the effect of the anisotropy of the core on high molecular Rydberg states is studied by quantum dynamics. It is found that on the time scale which can be probed by zero kinetic energy spectroscopy there is extensive interseries mixing. In particular, the long decay times are due to the sojourn in Rydberg series which are not directly effectively coupled to the continuum. These are series built on higher rotationally excited states of the core and a dynamical bottleneck controls the coupling to the bound series directly coupled to the ionization continuum. The computations are carried out for realistic molecular parameters and in the presence of a weak external de field. The quadrupolar coupling is often more effective in interseries coupling than the dipolar anisotropy even though the latter has a far higher range. The external field exhibits the expected {\textquoteleft}{\textquoteright}dilution{\textquoteright}{\textquoteright} or {\textquoteleft}{\textquoteright}time stretching{\textquoteright}{\textquoteright} effect at short times (of the order of the Stark period) but enhances the interseries mixing at longer times. An incomplete I mixing is the origin of another dynamical bottleneck. The time evolution is described both by exact quantum propagation and by a reduced description where degenerate states (i.e., states which differ only in the magnetic quantum numbers) are taken to be equally populated, on the average. This grouping, valid at longer times, facilitates the quantal computations which include several series with the full complement of angular momentum states of the electron. Such computations are possible by taking advantage of the conservation of the (total projection) quantum number M. For higher values of IM the coupling to the continuum is very much hindered and the bound Rydberg series exhibit extreme stability. The paper concludes by an analysis of the three bottlenecks which can give rise to longer decays. (C) 1996 American Institute of Physics.}, issn = {0021-9606}, doi = {10.1063/1.472308}, author = {Remacle, F. and LEVINE, RD} } @article { ISI:A1996VJ53900030, title = {Comment on the inversion of Raman excitation profiles}, journal = {CHEMICAL PHYSICS LETTERS}, volume = {260}, year = {1996}, month = {SEP 27}, pages = {507-510}, abstract = {The unique amplitude obtained by an inversion of an observed Raman excitation profile is one of minimal phase. As the frequency varies, the phase of such an amplitude can span a range larger than 2 pi. Therefore such an inversion can yield an amplitude that accurately reproduces the input profile. It is possible to add to the minimal phase additional terms but such modifications of the phase of the Raman amplitude cannot change the corresponding Raman excitation profile. Hence such terms cannot be determined from the profile and introducing them does not constitute an inversion procedure.}, issn = {0009-2614}, doi = {10.1016/0009-2614(96)00891-3}, author = {Remacle, F. and LEVINE, RD} } @article { ISI:A1996TT36100019, title = {Dynamics of Rydberg states of molecules in the intermediate regime: The role of the vibrations}, journal = {JOURNAL OF CHEMICAL PHYSICS}, volume = {104}, year = {1996}, month = {FEB 1}, pages = {1937-1952}, abstract = {The coupling of a Rydberg electron to the vibrational motion is discussed in the intermediate regime in which the orbital period is long on the scale of the vibrational motion but is still considerably faster than the rotation of the core. Two dimensionless variables characterize the dynamics: the ratio of time scales and the action exchanged between the electron and the core, per one revolution. The classical dynamics are reduced to a map which provides a realistic approximation in the limit when the action exchanged is larger than h. There are two distinguishable time regimes, that of prompt processes where the corresponding spectrum is so broad that individual Rydberg states cannot be resolved and a much slower process, where the electron revolves many times around the core before it ionizes. The overall spectrum is that of a Rydberg series, where the lines are broadened by (the delayed) vibrational autoionization superimposed on a broad background. The semiclassical dynamics is quantitatively more accurate in the typical situation when the action exchanged is comparable or smaller than h. Explicit analytical expressions are obtained for the width for vibrational autoionization including for the case when resonances are possible. The presence of resonances is evident in Rydberg lines which are broader. For low Rydberg states the present approach recovers the Herzberg-Jungen approximation in the weak coupling limit. (C) 1996 American Institute of Physics.}, issn = {0021-9606}, doi = {10.1063/1.470948}, author = {Rabani, E and LEVINE, RD} } @article { ISI:A1996VF84100003, title = {Dynamics of the collisional electron transfer and femtosecond photodissociation of NaI on ab initio electronic energy curves}, journal = {CHEMICAL PHYSICS LETTERS}, volume = {259}, year = {1996}, month = {SEP 6}, pages = {252-260}, abstract = {Ab initio dynamics on more than one electronic state is reported for the NaI system. This requires both a method for computing the electronic energy curves and their coupling and a matched method for propagating the equations of motion for the atoms. The long-range electron transfer (a {\textquoteleft}harpoon{\textquoteright} process) requires a particularly accurate electronic computation and many configurations are employed in a novel method which combines the advantages of the molecular orbital and valence bond approaches. The computation is performed {\textquoteleft}on the fly{\textquoteright} with the required electronic input being generated at each nuclear separation reached by the system.}, issn = {0009-2614}, doi = {10.1016/0009-2614(96)00765-8}, author = {Martinez, TJ and LEVINE, RD} } @article { ISI:A1996VM55400023, title = {First-principles molecular dynamics on multiple electronic states: A case study of NaI}, journal = {JOURNAL OF CHEMICAL PHYSICS}, volume = {105}, year = {1996}, month = {OCT 15}, pages = {6334-6341}, abstract = {We present the first application of first-principles molecular dynamics to a chemical process occurring on more than one electronic state. The example is the collisional chemi-ionization of NaI using a novel ab initio technique for the electronic states and a previously described full multiple spawning (FMS) classically motivated quantal method to describe the nuclear dynamics, The results for the dynamics are compared with fully exact quantal propagation, The FMS method which generates quantal amplitudes and inherently conserves normalization is shown to perform remarkably well for this heavy particle problem. The ab initio generated potentials and interstate couplings are compared with empirical potentials for NaI. Particular attention is given to the localized molecular orbital/generalized valence bond (LMO/GVB) method used for the electronic problem and to its interface with the equations of motion for the nuclei. The ability to incorporate atomic input (such as the ionization potential or the electron affinity) into the LMO/GVB method is emphasized. (C) 1996 American Institute of Physics.}, issn = {0021-9606}, doi = {10.1063/1.472486}, author = {Martinez, TJ and LEVINE, RD} } @article { ISI:A1995QK48700015, title = {CLASSICAL LIMIT OF THE DISTRIBUTION OF QUANTUM FLUCTUATIONS IN INTERMOLECULAR AND INTRAMOLECULAR DYNAMICS}, journal = {JOURNAL OF PHYSICAL CHEMISTRY}, volume = {99}, year = {1995}, month = {MAR 2}, pages = {2561-2567}, abstract = {A spectrum of final states can be produced in many ways; It can be a bound-bound process as in optical spectroscopy, a bound-continuum process as in photodissociation, or even a continuum-continuum transition as in a scattering experiment. A homogeneously broadened, resolved, spectrum exhibits variations in intensity which, while fully predictable by quantum dynamics, appear to the eye as {\textquoteleft}{\textquoteright}fluctuations{\textquoteright}{\textquoteright}. A phase space structure in which the statistical properties of such fluctuations can be examined is defined and discussed. In the classical limit, one recovers the results of {\textquoteleft}{\textquoteright}surprisal analysis{\textquoteright}{\textquoteright}. In the more general case, one obtains an extension to situations where quantal interference effects can be important.}, issn = {0022-3654}, doi = {10.1021/j100009a014}, author = {LEVINE, RD} } @article { ISI:A1995QE00500019, title = {POTENTIAL-ENERGY SURFACE EFFECTS ON DIFFERENTIAL CROSS-SECTIONS FOR POLYATOMIC REACTIONS}, journal = {CHEMICAL PHYSICS}, volume = {191}, year = {1995}, month = {FEB 1}, pages = {223-233}, abstract = {The effect on differential and integral cross sections of varying the potential energy of the entrance channel to a polyatomic reaction is investigated theoretically. The rotating bond approximation (RBA) is used for the CH4 + OH {\textendash}> CH3 + H2O reaction. The reaction exhibits peripheral dynamics, with a higher reactivity at higher impact parameters. Due to the significant potential barrier the scattering of the products is however sideways and not forward. It is found that varying the long-range isotropic terms in the potential has almost no effect on the opacity function or the cross sections. The addition of long range anisotropic terms induces rotational transitions of the OH reactant and thereby reduces the reactivity at higher impact parameters, resulting in backward scattering.}, issn = {0301-0104}, doi = {10.1016/0301-0104(94)00368-K}, author = {NYMAN, G and CLARY, DC and LEVINE, RD} } @article { ISI:A1995RX45600010, title = {SHATTERING OF CLUSTERS UPON SURFACE IMPACT - AN EXPERIMENTAL AND THEORETICAL-STUDY}, journal = {PHYSICAL REVIEW LETTERS}, volume = {75}, year = {1995}, month = {OCT 2}, pages = {2670-2673}, abstract = {{{The shattering transition expected upon ultrafast heating has been observed in size selected (NH3)(n-1)NH4+ clusters}, issn = {0031-9007}, doi = {10.1103/PhysRevLett.75.2670}, author = {HENDELL, E and Even, U and Raz, T and LEVINE, RD} } @article { ISI:A1995RP92800003, title = {KINETICS AND DYNAMICS OF REACTIONS IN LIQUIDS}, journal = {INTERNATIONAL REVIEWS IN PHYSICAL CHEMISTRY}, volume = {14}, year = {1995}, month = {SEP}, pages = {215-270}, abstract = {We discuss the control of the kinetics and dynamics of chemical reactions by the solvent, from a molecular point of view. The kinetics are discussed using a transition state theory (TST) approach, applied to the reactants and their surrounding solvent as one supramolecule. The topics discussed include a molecular interpretation for the changes that take place when one solvent is being replaced by another; the use of local against normal vibrational modes and/or joint description, i.e., local modes for part of the system and normal modes for the other part; and the effect of pressure on the rate in solution. The notion of free volume and volume of activation is extended to a more general phase space in which geometrical volumes may overlap, the approximations that are inherent to cell theory are examined and a molecular interpretation for internal and chemical pressures is suggested. The link to the dynamics is provided by an analysis of the breakdown of TST due to diffusion/cage control of the rate of the reaction. A unified description which interpolates from activation control to diffusion control is presented with a special emphasis on the motion within the solvation cage. Results of molecular dynamics simulations for both activated and activationless reactions are presented. The very detailed computer experiment is interpreted using a reduced mechanical description and the separation of time-scales is discussed using an adiabatic separation of variables. Spectroscopic methods for probing the different time epochs are suggested. The rather short duration typical of the motion within the solvent cage is emphasized, and the possibilities that this affords for studying the short-time dynamical role of the solvent via experiments in clusters or in glasses are noted.}, issn = {0144-235X}, doi = {10.1080/01442359509353310}, author = {BENNUN, M and LEVINE, RD} } @article { ISI:A1995QW39200034, title = {OVERLAPPING RESONANCES, MULTIPLE TIME REGIME EVOLUTION LAWS AND THE SAMPLING OF PHASE-SPACE IN UNIMOLECULAR PROCESSES}, journal = {JOURNAL OF THE CHINESE CHEMICAL SOCIETY}, volume = {42}, year = {1995}, month = {APR}, pages = {381-392}, abstract = {Unimolecular processes can be described as the decay of an ensemble of N excited resonances coupled to K decay channels. Resonances are metastable states characterized by a complex energy whose real part is the position of the state along the energy axis while the imaginary part gives the individual decay rate of the state. Resonances usually overlap in the RRKM regime. The degree of overlap is measured by the parameter R = /dE where is the average of the individual decay rates of the excited resonances and dE is the average spacing between their position. In the exact degeneracy limit, that is, for an infinite value of R, (N-K) resonances have a zero width, so that a fraction of the initial excitation remains permanently trapped in the bound subspace. This trapping effect subsists in the non degenerate case but is not complete. We use a random coupling effective Hamiltonian model to discuss the effect of the degree of overlapping R, and of the number of resonances N and decay channels K, on the temporal evolution laws of the bound subspace and of the fragments. The decay law of the bound subspace and the temporal evolution of the yields in fragments exhibit several time regimes. This is due to the fact that after the diagonalization of the effective Hamiltonian, the decay widths of the resonances cluster into one group of K large widths and one group of(N-K) small ones. The trapping effect is due to the (N-K) small widths. The amount of trapping depends on the value of the degree of overlapping R, and for a given value of R, on the ratio N/K: large values of R and of N/K correspond to a large amount of trapping in the bound subspace for times long when compared to h/. The temporal evolution laws of the yields in fragment are also strongly affected by the degree of overlapping and the value of the ratio N/K. Due to the reorganization of the partial widths which follows the diagonalization of the effective Hamiltonian, we show that the nature of the dominant product can change while increasing the value of R and N/K. We also discuss the time evolution of the sampling of phase space for a specific preparation in terms of these two parameters. The volume sampled is computed using an entropic measure. When the resonances overlap, there is not enough time to completely sample phase space prior to dissociation. The fraction sampled decreases as the amount of trapping in the bound phase space increases.}, issn = {0009-4536}, author = {Remacle, F. and LEVINE, RD} } @article { ISI:A1995QV74800010, title = {A QUANTITATIVE MODEL FOR THE DYNAMICS OF HIGH RYDBERG STATES OF MOLECULES - THE ITERATED MAP AND ITS KINETIC LIMIT}, journal = {BERICHTE DER BUNSEN-GESELLSCHAFT-PHYSICAL CHEMISTRY CHEMICAL PHYSICS}, volume = {99}, year = {1995}, note = {Meeting of the Deutsche-Bunsen-Gesellschaft-fur-Physikalische-Chemie on Molecular Spectroscopy and Molecular Dynamics - Theory and Experiment, GRAINAU, GERMANY, AUG 28-SEP 01, 1994}, month = {MAR}, pages = {310-322}, publisher = {DEUT BUNSEN GESELL PHYSIKAL CHEM}, abstract = {An iterated map which mimics the dynamics of a high Rydberg electron revolving around an anisotropic ionic core is described. The map specifies the change in the quantum numbers of the electron due to its passage near to the rotating core. Attention is centered on the limiting case of physical interest where the rotation of the core is faster than the orbital motion of the electron. While the map does provide for a very efficient way to numerically simulate the motion, its main advantage is in that it delineates the various dimensionless coupling parameters that govern the dynamics. To make contact with many experiments, external electrical and magnetic fields are included in the Hamiltonian. The stretch of the kinetic time axis due to the presence of external fields is discussed. The full map can be further approximated by a one-dimensional map which captures the essence of the dynamics. The primary aspects having to do with the three-dimensional character of the actual motion are incorporated in the magnitude of the dimensionless coupling parameters. A simple but realistic limit of the one-dimensional map is discussed which can be considered as the electron undergoing diffusion in its energy. The mean first passage time out of the detection window and the branching fractions for ionization vs. stabilization of the electron are computed in the diffusion approximation. As is experimentally observed, the lifetime of the high Rydberg states exhibits a maximal value when plotted vs. the energy.}, issn = {0005-9021}, author = {Rabani, E and LEVINE, RD and Even, U} } @article { ISI:A1995QY25200036, title = {4-CENTER REACTIONS - A COMPUTATIONAL STUDY OF COLLISIONAL ACTIVATION, CONCERTED BOND SWITCHING, AND COLLISIONAL STABILIZATION IN IMPACT HEATED CLUSTERS}, journal = {JOURNAL OF PHYSICAL CHEMISTRY}, volume = {99}, year = {1995}, month = {MAY 11}, pages = {7495-7506}, abstract = {Molecular dynamics simulations are presented showing that four-center reactions with high activation barriers occur readily, and in a concerted manner, under conditions of cluster impact. At the high velocities which prevail inside an impact heated cluster, we show that one can conveniently examine the reactive event as a sequence of elementary, suddenlike steps. The importance of the timing of these steps is emphasized. The bond-switching step is described by a kinematic model, which is shown to account for the energetic and steric requirements and for energy disposal of the concerted four-center reaction. Three different cases are examined in detail: the bimolecular N-2 + O-2 and H-2 + I-2 reactions and the unimolecular norbornadiene {\textendash}> quadricyclane isomerization. The cluster is shown to have a significant role not only in activating the reactants but, equally important, in stabilization of the energy-rich nascent products. The event is over when the cluster beings to fragment, which occurs after a small number of collisions of its constituents. Comparison is made between clusters of different rare gases. In terms of the overall reactivity, all rare gases are similar and the role of the mass can be compensated by a suitable scaling of the initial velocity of impact. There are, however, differences related to the mass ratio of the reactants to that of the rare-gas atom. The high yield of the four center concerted mechanism in impact heated clusters and the very essential role of the cluster in overcoming the constraints on such a mechanism suggest that the designation {\textquoteleft}{\textquoteright}cluster catalyzed reaction{\textquoteright}{\textquoteright} is appropriate.}, issn = {0022-3654}, doi = {10.1021/j100019a035}, author = {Raz, T and LEVINE, RD} } @article { ISI:A1995QD03300016, title = {DYNAMICS AND KINETICS OF MOLECULAR HIGH RYDBERG STATES IN THE PRESENCE OF AN ELECTRICAL-FIELD - AN EXPERIMENTAL AND CLASSICAL COMPUTATIONAL STUDY}, journal = {JOURNAL OF CHEMICAL PHYSICS}, volume = {102}, year = {1995}, month = {JAN 22}, pages = {1619-1638}, issn = {0021-9606}, doi = {10.1063/1.468894}, author = {Rabani, E and LEVINE, RD and MUHLPFORDT, A and Even, U} } @article { ISI:A1995TH20500013, title = {SHORT-TIME DYNAMICS ON SEVERAL ELECTRONIC STATES - FORMALISM AND COMPUTATIONAL STUDY OF I-2 IN RARE-GAS SOLVENTS}, journal = {CHEMICAL PHYSICS}, volume = {201}, year = {1995}, month = {DEC 1}, pages = {163-187}, abstract = {A computationally tractable approximation for both interstate and intrastate dynamics is derived and applied. The correlation between the electronic and nuclear degrees of freedom is explicitly allowed for in that there is an equation of motion for the nuclear dynamics on each electronic state. These equations for the intrastate dynamics are coupled due to the interstate interaction. The exact equations are derived from a quantum mechanical Hamiltonian and are then simplified by assuming that the coupling between the different electronic states is localized and that, in the absence of interstate coupling, the nuclear motion on each electronic state is classical-like. Equations for the populations and the phases of the different electronic states are also derived. Coupling of the nuclear modes to a classical solvent is included in the formalism and the main computational effort is in the mechanical description of the solvent. As a computational example, a simulation of a fast pump-fast probe for an iodine X {\textendash}> B (bound) transition, in rare gas solvents, is presented and discussed. Despite the long range of the B state potential of iodine, which enhances the effect of the solvent on the excited state dynamics, there is a finite delay before the coupling to the solvent is manifested. The delocalization of the optically prepared state markedly slows down as the density is lowered. At longer times there is considerable energy exchange with the solvent. As a result many molecules either gain enough energy to dissociate or are cooled down, depending on the temperature and density of the solvent. At the higher densities, many molecules which attempt to dissociate are caged.}, issn = {0301-0104}, doi = {10.1016/0301-0104(95)00240-0}, author = {BENNUN, M and LEVINE, RD} } @article { ISI:A1995TE58800017, title = {PROMPT SOLVENT-INDUCED ELECTRONIC PREDISSOCIATION OF FEMTOSECOND PUMPED IODINE - A COMPUTATIONAL STUDY}, journal = {CHEMICAL PHYSICS LETTERS}, volume = {245}, year = {1995}, month = {NOV 10}, pages = {629-638}, abstract = {Solvent-induced electronic predissociation (X {\textendash}> B {\textendash}> al(g)((3) Pi) state) of molecular iodine is discussed using a classical ensemble representation of Heisenberg{\textquoteright}s equations of motion. Excitation of the intermediate B state by an ultrafast pulse creates a coherent vibrational motion in this bound state. The localized solvent-induced coupling to the a state results in the spawning of dissociation products which occurs in bursts, twice per vibrational period. Equations of motion for both the electronic and nuclear degrees of freedom in each electronic state are derived from a quantum mechanical Hamiltonian. These equations are coupled whenever two electronic states are interacting. The formalism includes coupling to the surrounding classical solvent. Comparison with a pump-probe experiment is provided.}, issn = {0009-2614}, doi = {10.1016/0009-2614(95)01064-G}, author = {BENNUN, M and LEVINE, RD and JONAS, DM and Fleming, G. R.} } @article { ISI:A1995TH24400008, title = {ON THE BURNING OF AIR}, journal = {CHEMICAL PHYSICS LETTERS}, volume = {246}, year = {1995}, month = {DEC 1}, pages = {405-412}, abstract = {Air is shown to burn (in theory, using two complementary procedures) under the unusual combination of conditions made possible within a cluster heated by a supersonic impact at an inert surface. Both clusters of neat N-2/O-2 and clusters containing several N-2 and O-2 molecules within a rare gas envelope have been studied. The principal reaction is N-2+ O-2 {\textendash}> 2NO which proceeds via a four-center mechanism. The four-center reaction N-2 + O-2 {\textendash}> N2O + O leads to N2O which is quite hot, as is to be expected on the basis of kinematic considerations, and is efficiently destroyed as the cluster expands. During the early, compression, stage multi- (>4) center reactions readily occur. The results of molecular dynamics simulations using a many-body potential are well accounted for by a distribution of products of maximum entropy subject to conservation of energy, matter and charge.}, issn = {0009-2614}, doi = {10.1016/0009-2614(95)01144-4}, author = {Raz, T and LEVINE, RD} }