We study the photodissociation of the H+2 molecule by ultrashort Fock-state electromagnetic pulses (EMPs). We use the Born-Oppenheimer treatment combined with an explicit photon number representation via diabatic electrophoton potential surfaces for simplification of the basic equations. We discuss the issue of the number of photon states required and show that six photon states enable good accuracy for photoproduct kinetic energies of up to 3 eV. We calculate photodissociation probabilities and nuclear kinetic-energy (KE) distributions of the photodissociation products for 800 nm, 50-TW/cm2 pulses. We show that KE distributions depend on three pulse durations of 10, 20, and 45 fs and on various initial vibrational states of the molecule. We compare the Fock-state results to those obtained by “conventional,” i.e., coherent-state, laser pulses of equivalent electric fields and durations. The effects of the quantum state of EMPs on the photodissociation dynamics are especially strong for high initial vibrational states of H+2. While coherent-state pulses suppress photodissociation for the high initial vibrational states of H+2, the Fock-state pulses enhance it.

Producing and controlling nonclassical light states are now the subject of intense experimental efforts. In this paper we consider the interaction of such a light state with a small molecule. Specifically, we develop the theory and apply it numerically to calculate in detail how a short pulse of nonclassical light, such as the high intensity Fock state, induces photodissociation in H2+. We compare the kinetic energy distributions and photodissociation yields with the analogous results of quasi-classical light, namely a coherent state. We find that Fock-state light decreases the overall probability of dissociation for low vibrational states of H2+ as well as the location of peaks and line shapes in the kinetic energy distribution of the nuclei.

Characterizing and localizing electronic energy degeneracies is important for describing and controlling electronic energy flow in molecules. We show, using topological phase considerations, that the Renner effect in polyatomic molecules with more than three nuclei is necessarily accompanied by 'satellite' conical intersections. In these intersections the non-adiabatic coupling term is on average half an integer. We present ab initio results on the tetra-atomic radical cation C2H+2 to demonstrate the theory.

We reconsider the Born-Oppenheimer-Huang treatment of systems of electrons and nuclei for the case of their interaction with time-dependent fields. Initially, we present a framework in which all expressions derived are formally exact since no truncations are introduced. The objective is to explore the general structure of the equations under the most unrestricted conditions, including the possibility that the electronic basis is dependent both on the nuclear coordinates and on time. We then derive an application of the theory applicable to cases of interaction with strong time-dependent fields. The method truncates the electronic basis only after the time-dependent interaction is taken into account in the electronic wave functions. This leads to theory which is similar to a Born-Oppenheimer-type truncation within the interaction picture. (C) 2003 American Institute of Physics.

Recently the Jahn-Teller model was extended to treat (reactive) scattering processes. The present study is devoted to possible effects of a degenerate vibronic coupling (DVC) on resonances. The main conclusions are: (a) The DVC affects dramatically the state-to-state transition processes and as a result it shuffles resonances attached to given transitions and may cause existing resonances to be masked by other processes. (b) The DVC may affect the widths and the heights of resonances but change only slightly their position.