The Lindblad master equation is a fundamental tool for describing the evolution of open quantum systems, but its computational complexity poses a significant challenge, especially for large systems. This article introduces a stochastic representation of the Lindblad dissipator that addresses this challenge by bundling the Lindblad operators. The stochastic dissipator maintains the Lindblad form, ensuring completely positive and trace-preserving dynamics. We demonstrate the effectiveness of this method by considering a Morse oscillator coupled to a spin bath. Our numerical experiments show that a small number of stochastically bundled operators can accurately capture the system’s dynamics, even when the Hilbert space dimension is large. This method offers a new perspective on open quantum systems and provides a computationally efficient way to simulate their dynamics.

Proton-transfer dynamics in hydrogen-bonded dimers are important for understanding debated mechanisms of radiation damage to DNA base pairs. Using coincidence photofragment imaging in ultrafast extreme-ultraviolet pump and near-IR probe experiments on the formic acid dimer, we observed a transient enhancement (150 fs) of the protonated monomer signal. This correlates with ab initio molecular dynamics simulations of the ionization induced dynamics, showing concerted proton transfer and dimer ring opening in a metastable dimer. Coincidence analysis revealed the ultraslow mechanism of the metastable dimer cation on the microsecond time scale. The ultraslow dynamics were attributed to a barrier for the structural rearrangement of the deprotonated moiety from an HCOO to an OCOH geometry. Moreover, ultraslow channels of protonated monomer ions to form H3O+ + CO and H2O + CHO+ were observed and interpreted as dissociation of hot photoions, involving nontrivial hydrogen migration.

Engineered metallic nanoparticles, which are found in numerous applications, are usually stabilized by organic ligands influencing their interfacial properties. We found that the ligands affect tremendously the electrochemical peak oxidation potentials of the nanoparticles. In this work, identical gold nanoparticles were ligand-exchanged and carefully analyzed to enable a precise and highly reproducible comparison. The peak potential difference between gold nanoparticles stabilized by various ligands, such as 2and 4-mercaptobenzoic acid, can be as high as 71 mV, which is substantial in energetic terms. A detailed study supported by density functional theory (DFT) calculations aimed to determine the source of this interesting effect. The DFT simulations of the ligand adsorption modes on Au surfaces were used to calculate the redox potentials through the thermodynamic cycle method. The DFT results of the peak potential shift were in good agreement with the experimental results for a few ligands, but showed some discrepancy, which was attributed to kinetic effects. The kinetic rate constant of the oxidation of Au nanoparticles stabilized by 4mercaptobenzoic acid was found to be twice as large as that of the Au nanoparticles stabilized by citrate, as calculated from Laviron’s theory and the Tafel equation. Finally, these findings could be applied to some novel applications such as determining the distribution of nanoparticle population in a dispersion as well as monitoring the ligand exchange between nanoparticles.