A SEMICLASSICAL STUDY OF GAS SOLID ENERGY-TRANSFER - HE, NE, AND AR ON METAL-SURFACES

A recently developed fully quantum theory of gas-surface energy transfer has been modified to treat systems where the wave function of the scattering molecule is written in terms of time dependent Gaussian wave packet basis functions. This allows for the inclusion of surface temperature effects in the systems studied using these techniques. The treatment is fully multiphonon, and can be applied to systems where the coupling of the gas particle to the vibrations of the solid is anywhere from weak to strong. Equations of motion are derived for the parameters which described each wave packet. In the limit we ignore the widths and phases of these wave packets, the remaining equations for the average position and momentum describe a classical trajectory coupled to a bath of quantum mechanical oscillators. Unlike earlier forms of this theory, our molecular trajectory has proper temperature dependence. Expressions are derived for both the sticking probability, and P(ΔE), the probability that a scattering particle exchanges and amount of energy ΔE with the solid. The dependence of these probabilities on the surface temperature, particle mass, particle energy, angle of incidence, and the interaction potential are examined for He, Ne, and Ar scattering from Cu(100). Comparison is also made with recent experimental studies of Ar on Ni and Ir. Reasonable agreement is found for average scattered beam energies and trapping probabilities. © 1990 American Institute of Physics.