A method is presented for calculating elastic and inelastic scattering probabilities for light particles, such as helium and molecular hydrogen, scattering from surfaces with which they weakly interact. The method is a unitary one-phonon approximation in which the scattering probabilities are calculated from thermally averages amplitudes which are generated numerically. The thermal averaging procedure is more general than this application and could be applied to other systems with weak inelastic scattering. An approximation for the gas surface interaction potential is discussed that can greatly simplify calculations where it is applicable. Finally some preliminary results are presented using this method to study rotationally mediated selective adsorption resonances in HD scattering from copper.

Dynamics of Gas-Surface Scattering deals with the dynamics of scattering as inferred from known properties of gases and solids. This book discusses measurements of spatial distributions of scattered atomic and molecular streams, and of the energy and momentum which gas particles exchange at solid surfaces. It also considers two regimes of scattering, both of which are associated with a lower range of incident gas energies: the thermal and structure scattering regimes. Comprised of 10 chapters, this book opens with a brief historical overview of the early experiments that investigated the dynamics of scattering of gases by surfaces. The discussion then turns to some elements of the kinetic theory of gases; intermodular potentials and interaction regimes; and classical-mechanical lattice models used in gas-surface scattering theory. The applications of molecular beams to the study of gas-surface scattering phenomena are also described. The remaining chapters focus on experiments and theories on scattering of molecular streams by surfaces of solids, with emphasis on thermal and structure regimes of inelastic scattering; quantum theory of gas-surface scattering; and quantum mechanical scattering phenomena. This text concludes with an analysis of energy exchange processes that may occur when a solid surface is completely immersed in a still gas. This monograph will be a valuable resource for students and practitioners of physics, chemistry, and applied mathematics.

Helium and molecular hydrogen scattering from copper is calculated to examine general features of scattering for these systems, especially the quantum mechanics of the scattering process, both for the motion of the particle and the excitations of the lattice. These calculations use an interaction potential chosen to simplify the numerical calculation while retaining the essential physics of the interaction. The scattering calculations show that these approximations quantitatively reproduce experimental results. The scattering probabilities are shown to depend on details of the system like the well depth and the steepness of the potential and assumptions are made to simplify the interaction potential. H2 and D2 inelastic scattering and trapping probabilities show strong enhancement by selecti adsorption resonances and overall changes in scattering intensities due to other more subtle effects of the rotational degrees of freedom. Temperature dependent HD scattering probabilities show the effect of inelastic scattering on rotationally inelastic scattering and selective adsorption resonances.

Interface phenomena are most fascinating because of the mixing of different scales and the interference of diverse physical processes. This makes it necessary to use different levels of description: microscopic, kinetic, and gas-dynamical. A unified quasiclassical approach is used to answer practical questions dealing with inelastic gas-surface scattering, the kinetics of adsorption layers, the evolution of inhomogeneities and defects at the surface, the Knudsen layer, the development of boundary conditions on the kinetic and gas-dynamical levels, the determination of exchange and slip coefficients, and so on.