Velocity distribution measurements of 0.06–1.4 eV argon and neon atoms scattered from the (111) plane of a silver crystal

Abstract

Velocity distribution and out‐of‐plane density distribution measurements are reported in detail for 0.6–1.4 eV argon and neon atoms scattered from the (111) plane of single silver crystals. Incident energies were selected to probe the regime of epithermal scattering where significant changes in scattering direction were previously found to occur. Velocity and density distributions are combined and integrated to yield total transfer coefficients. The change in scattering direction is found not to be related to a transition to structurescattering but rather to a decrease in normal momentum transfer as the total scattering becomes more elastic.Structurescattering effects are more apparent in differential momentum transfer data which show a transfer of momentum from normal to tangential components, in agreement with calculations by McClure. The width of the scattering would therefore be a better parameter to indicate structural effects. An anomaly in the direction of energy transfer also appears which suggests that energy may be transferred from the crystal to the gas even though the mean incident energy may be greater than the mean lattice energy. In general the qualitative results of McClure for differential momentum transfer and of Oman for integrated transfer characteristics of the specific argon‐silver interaction appear to be substantially correct.