Inelastic energy loss in large angle scattering of Ar9+ ions from Au(111) crystal

The azimuthal angle dependence of the energy loss in large-angle scattering of slow (nu approximate to 0.06 a.u.) Ar9+ ions from a Au(1 1 1) single crystal was investigated. Regarding the kinematics of quasi-single collisions, the smallest energy loss is expected for the azimuthal orientations which correspond to the closest packed atomic row of the crystal. This agrees with the prediction of a trajectory simulation (Marlowe code), but the experimental results don't show such dependence. Thus, we discuss possible inelastic processes as image charge energy gain, electronic energy loss in close collision and the electronic energy loss in the interaction with the electron gas. The observed azimuthal dependence is explained by the change of the electronic stopping power due to the variation of effective electron density sampled by the projectile. (C) 2003 Elsevier Science B.V. All rights reserved.