A semiclassical surface-hopping procedure for vibrational relaxation in polyatomic molecules: model calculations

In this paper, the application to polyatomic systems of a semiclassical surface-hopping theory for the calculation of vibrational transition probabilities and rates is explored through the use of simple model systems. The theory has previously been applied to relaxation of vibrational excitation energy in diatomics. The non-adiabatic coupling is analyzed for the polyatomic case. Two systems are considered. One of these, which qualitatively mimics CO2 in Ar, has a strongly bonded triatomic. In the other system, which roughly models KrF2 in Ar, the triatomic is a comparatively weakly bonded molecule, and the solvent interactions are relatively more significant. Results of calculations using this theory are compared with calculations based on approximations to the full theory. These approximations have previously been found to provide a very computationally facile procedure for the calculation vibrational relaxation rates of diatomic molecules in condensed-phase systems. (Copyright (c) 1999 Elsevier Science B.V., Amsterdam. All rights reserved.)