Classical and quantum-mechanical models of thermal and flash desorption of atoms from surfaces

Abstract

Two models, one classical and the other quantum-mechanical, for nonequilibrium thermal and flash desorption of atoms and molecules from surfaces are proposed, and their predictions are compared with those of previous (classical) models (of thermal desorption). Deviations from the equilibrium dependencies, on desorption angle, of (a) the desorbing atomic flux, (b) the average energy of desorbing atoms, and (c) the desorbing atomic speed ratio are found, these deviations being generally less pronounced than, and sometimes qualitatively opposite from, those predicted by previous models. The classical model lends itself to relatively easy calculations of atom-surface sticking probabilities, and several examples of these results are presented; apart from their intrinsic interest, they also serve as useful checks on the model calculations. Analogous calculations are not possible on the present form of the quantum-mechanical model.