Nonadiabatic molecular dynamics simulation of photodissociation and geminate recombination of I-2 liquid xenon

In this paper we investigate the B state predissociation and subsequent geminate recombination of photoexcited iodine in liquid xenon using a coupled quantum-classical molecular dynamics method and a model Hamiltonian gained from the diatomics-in-molecules semiempirical approach to excited state electronic structure including spin-orbit coupling. We explore the capabilities of these techniques as applied to studying the dynamics of realistic condensed phase reactions by comparing with available experimental data from recent ultrafast spectroscopic studies and Raman scattering measurements. We present a microscopic understanding of how the solvent perturbs the electronic states of the chromophore and opens various channels for dissociation from the bound excited B state. We survey the different possible dissociative channels and determine their relative importance as a function of solvent density. We find that predissociation usually occurs during the first bond extension within about 50-100 fs. We follow our trajectories out to 2 ps and observe early solvent collisions which, at the highest solvent densities studied, often result in geminate recombination to the excited bound A' state with in this time. (C) 1996 American Institute of Physics.