Angular dependence of energy loss in scattering of slow highly charged Ar ions from a Au surface

Abstract

We have studied the energy loss of slow (velocity v≈0.06 a. u. ) highly charged Ar 9+ ions scattered at large angles from a clean Au(1 1 1) single crystal surface. The influence of the scattering geometry on the energy loss has been investigated for different incidence angles ( 5°⩽ψ⩽37.5°) and scattering angles ( 30°⩽θ⩽75°). At large angles ( ψ= 37.5°, θ= 75°), the main peak in the measured energy spectrum agrees well with the position expected for binary elastic scattering. With decreasing incidence angle a shift of the “binary peak” to lower energy is observed, and for decreasing scattering angles, a shift of the binary peak to higher energy than calculated by kinematics is found. The additional energy loss seen at small ψ ( ψ= 5°) is interpreted by inelastic energy loss. A model calculation which combines s rate-equation description of Auger cascades, recapture to the surface with a Firsov type model and image charge acceleration during ion–surface interaction is used to describe the data.