Scattering of 0.05–5-eV Argon from the (111) Plane of Silver

Abstract

The scattering of atomic beams of argon from the (111) plane of silver has been measured for incident energies in the range of 0.05–5 eV. Nearly monoenergetic beams were produced by the use of nozzle sources with pure argon and mixtures of argon with helium or hydrogen. Epitaxially grown crystal surfaces were obtained by vapor deposition of silver on mica. The observed scattering patterns were single lobes with the maxima lying near the specular angle at all energies. Results were similar to those of Smith, Saltsburg, and Palmer at energies below 0.3 eV with the maxima shifting toward the tangent to the surface with increasing energy. At higher energies the maxima were observed to shift back toward the normal as predicted by the theoretical calculations by Oman. Comparison of results with the simple hard- and soft-cube models for scattering indicates limitations of these models at hyperthermal energies.