A semiclassical model for atomic scattering from solid surfaces—He and Ne scattering from W(112)

Abstract

A semiclassical formalism is presented which predicts specular atomic scattering from close-packed surfaces and either ’’rainbow’’ or diffractive scattering from strongly periodic surfaces. The intensities are a series of δ functions at the Laue conditions modulated by the product of the classical intensities and a structure factor accounting for interference among multiple trajectories within a unit cell. Narrow energy distributions in the incident beam and/or long wavelengths result in well-resolved diffracted beams, while broad distributions and/or small wavelengths result in coalesced beams which display only the ’’rainbowlike’’ intensity envelope. A simple elastic model using a 6–9 potential has been used to predict He and Ne scattering from W(112). For helium the peak positions and relative peak heights agree with the measured scattering essentially within experimental reproducibility, but the peak widths calculated with this elastic model are too narrow and the intensity maxima too large. Neon calculations reproduce qualitatively the rainbow patterns observed in the experiments but neither the intensities nor the positions of the rainbow features are correct, indicating the existence of large inelastic effects.