Scattering of Helium and Argon from the Cleavage Plane of Lithium Fluoride

Abstract

The scattering of helium and argon from the cleavage plane of lithium fluoride has been studied using molecular-beam techniques and under vacuum conditions which were somewhat better than are typical for systems of this type. The helium measurements confirm the diffraction effects reported by O. Stern and co-workers and reveal, in addition, a broad scattered beam approximately symmetrical about the specular position which apparently has not been previously recognized. Measurements with argon beams gave scattering patterns which were quite different from those obtained for helium. The scattered beams were very broad and had an intensity maximum between the specular position and the crystal normal. Analysis of the data showed that this deviation of the maximum from the specular position cannot be obtained by superposition of specular and cosine-law scattering components. Furthermore, the experimental data on the scattering of argon seem to be inconsistent with a diffraction mechanism.