Dissociative sticking of diatomic molecules on cold, non-rigid surfaces: comparison of quantal and semiclassical surface oscillator models

The influence of a moving substrate on the dissociative sticking probability of diatomic molecules is investigated with the help of time-dependent quantum dynamical methods. The dissociating molecule is treated as a wave packet, whereas the moving surface is idealized as a set of quantal and classical generalized Langevin-oscillators, respectively. By comparing quantal with classical single-Einstein oscillator models, a systematic estimate of the errors introduced when the surface motion is approximated by classical mechanics becomes possible. Further, by comparing classical single- to multiple-oscillator models, the validity of the popular single oscillator treatment can be addressed. It is argued that, at least in the present model, it seems more important to include many surface oscillators approximately, rather than treating a single oscillator "exactly". (C) 1998 Elsevier Science B.V. All rights reserved.