Electronic and Solvent Relaxation Dynamics of a Photoexcited Aqueous Halide

Abstract

The details of the electronic and solvent relaxation dynamics following two-photon excitation of an aqueous halide ion are studied via nonadiabatic quantum molecular dynamics simulation. It is found that the branching ratio at very early times (<50 fs) between two channels, a minor channel involving direct electron detachment to a spatially separated solvent void and a dominant channel characterized by delayed adiabatic detachment following a cascade through excited electronic states of the ion, is determined by the effect of solvent dynamics on the values of the ionic and void electronic energies, as well as the relative small matrix elements for tunneling into void states. Solvent dynamics is also found to be important in controlling the rate of electron transfer which leads to geminate recombination of proximal electron−halogen atom pairs. The sensitivity of this recombination rate to the relative energy levels of the unoccupied valence electron hole on the solvated halogen and that of the hydrated ele...