Semiclassical wave packet studies of elastic and inelastic atom--surface scattering from a 3D model surface

The semiclassical wave packet method for the investigation of elastic and inelastic gas--surface scattering is extended to the calculation of diffraction patterns and Debye--Waller factors for scattering from a three-dimensional surface. Application of the method to a model 3D surface yields energy transfer coefficients in good accord with our previous 2D semiclassical results and with the experimental molecular beam data. The calculated final-state momentum and energy distributions are highly structured and show that inelastic effects dominate the scattering process at high surface temperatures. At T/sub s/ = 300 K, the scattering is found to be more nearly elastic. The structural features of the distributions are shown to be correlated with the power spectrum for the lattice motion. Diffractive scattering is evident even at T/sub s/ = 1500 K. At T/sub s/ = 300 K, the diffraction is much more pronounced due to the increased elasticity of the collision and a larger Debye--Waller factor. The positions of the calculated diffraction peaks are found to be in excellent accord with that expected from the known surface grating and distribution of incident wavelengths. The dependence of the computed Debye--Waller factors upon T/sub s/, the surface Debye temperature and the gas-surface potential well depth is found to be accurately described by the simplified expressions developed by Beeby and by Comsa et al. In general, the method is shown to be well suited to the study of elastic and inelastic gas--surface processes