Quantum effects in excitation spectra of desorbing hydrogen molecules

Abstract

A quantum mechanical approach to associative or recombinative desorption of diatomic molecules is described. The formulation is based on the concept of a reaction path and in principle allows prediction of the vibrational and rotational excitation of desorbing molecules. In this paper we first consider very light molecules such as H 2 and D 2 desorbing via a Langmuir-Hinshelwood reaction in some detail. In a simple model neglecting rotations the dependence of vibrational excitation on incident energy, the curvature of the reaction path and the position and height of the saddle point are studied. Various experimental results can be described with reasonable parameters. Vibrational excitation in Eley-Rideal reactions and rotational excitations in general are considered in a semiquantitative way.