Electron density at the Ag(110) surface studied by He diffraction

High-resolution helium-diffraction measurements from the Ag(110) surface, taken with beam energies $E_0$=17.8 meV and $E_1$=64.6 meV, angles of incidence ranging between 20° and 80°, and along the 〈001〉, 〈11¯0〉,and 〈11¯1〉 crystal directions, are presented. The scattering data allow a detailed description of the He-metal interaction energy. The unperturbed electron density of the metal surface, determined from the interaction energy by using the effective-medium theory, is found to be in disagreement with the overlapping of atomic densities. In agreement with Harris and Liebsch’s calculations [J. Phys. C 15, 2275 (1982); Surf. Sci. 123, 355 (1982)], the corrugation amplitudes of the isodensity surface are found to decay much faster than predicted by the overlapping of atomic densities.