Scattering of Low Energy Atoms by Surfaces: The Helium—Copper Systems

A number of experimental results for the diffraction of low energy helium by closely packed and stepped copper surfaces is presented. Observation of selective adsorption resonances shows that the surface average of the interaction potential is the same for all crystal faces. The thermal attenuation of the scattered intensities is given by a modified Debye—Waller factor. These results are interpreted in terms of interaction potentials with a soft exponential repulsion and an attractive well using an exact method based on Neumann iteration of the transition matrix equation. Good agreement with experiment is obtained in several systems over a large range of scattering energies.