Interaction potentials for fast atoms in front of Al surfaces probed by rainbow scattering

Rainbow scattering for grazing-angle incidence of atoms at surfaces along low-indexed channeling directions provides a sensitive probe of quasistatic atom-surface potentials. The dependence of the rainbow angle on the kinetic energy for the projectile motion perpendicular to the surface, E(1), varies with the electronic structure of the projectile as well as the crystallographic face of the aluminum surface. Comparison between experiment and classical Monte Carlo trajectory simulations demonstrates that the superposition of binary atom-atom potentials fails to adequately represent the equipotential surfaces. Ab initio atom-surface potentials based on density-functional theory are required to reach satisfactory agreement with experiment.