Dependence of the He-Scattering Potential at Surfaces on the Surface-Electron-Density Profile

It is shown that the repulsive part of the He-surface interaction is given by an almost linear, surface-independent function of the surface electron density at the He site. This gives a very simple connection between the measured low-energy He-beam scattering potentials and the substrate electron densities. The scheme is applied to an analysis of the He-scattering potential outside Al.