Scattering of Helium, Neon, Argon, Krypton, Xenon, and Deuterium from a Tungsten (110) Surface Characterized by LEED

Abstract

Rare gas (He, Ne, Ar, Kr, and Xe) scattering distributions have been measured from a tungsten (110) surface at an incidence angle of 45°. The gas temperature was 295°K, while the surface temperature varied between 375 and 1300°K. The positions of the peak maxima and the broadening of pseudospecular scattering of He and Ne correlate with the FRI models, whereas the Ar–Xe results are anomalous in that these aspects of the scattering do not correlate with either the FRI or soft-cube models because Ar, Kr, and Xe are dominated by trapping at the surface. An estimate of the fraction of the rare gas atoms initially trapped at the surface has been made. Deuterium scattering distributions have been measured and are characterized by a relatively large diffuse fraction which is attributed to an internal excitation of the diatomic molecule rather than to trapping at the metal surface. Comparisons of these data with scattering from the (111) face of fcc crystals suggests three phenomenologically distinguishable scattering regimes, quasielastic, inelastic, and trapping dominated scattering.