Solvent induced vibrational population relaxation in diatomics. II. Simulation for Br2 in Ar

Results are presented from a computer simulation of the population relaxation of the lowest (1→0) vibrational transition for a system of Br2 in a dense Ar fluid at 300 K. The calculate relaxation time is 253 ps. The method of calculation is a mixed quantum–semiclassical–classical simulation procedure. The vibrational state energies and wave functions are obtained from perturbation theory for fixed values of the rotational and translational variables. The relaxation rate for the vibrational transition is evaluated using a semiclassical surface hopping theory of nonadiabatic processes. The configurations of rotational and vibrational variables are sampled from a classical canonical ensemble density using standard Monte Carlo sampling. The relative efficiency of the rotations and translations in promoting the vibrational population relaxation is examined, and the use of perturbation theory and some assumptions of the model are tested numerically.