GENERALIZED BROWNIAN DYNAMICS .2. VIBRATIONAL-RELAXATION OF DIATOMIC-MOLECULES IN SOLUTION

A simple classical stochastic model for diatomic vibrational relaxation, based on the generalized Langevin equation, is presented. The memory function in the generalized Langevin equation is determined directly from equilibrium force autocorrelation functions for the individual atoms of the diatomic dissolved in the solvent of interest. A simple autoregressive (AR) procedure, developed in a preceding paper [D. E. Smith and C. B. Harris, J. Chem. Phys. 92, 1304 (1990)], is used for modeling the memory functions to arbitrary order. This model is tested on the system of iodine in Lennard-Jones xenon using fourth order AR approximations for the memory functions, and is found to be very effective in reproducing data from molecular dynamics simulations at two very different densities. Results are discussed in terms of the simplifying assumption that the solvent interaction with the diatomic can be characterized by equilibrium dynamics of single atoms in solution. © 1990 American Institute of Physics.