MULTIPLE-SCATTERING IN THE INTERACTION OF LOW-ENERGY IONS WITH A COLDAU SURFACE COVERED BY A FILM OF CONDENSED ARGON

Energy spectra of ions emitted from a cold (< 40 K) Au surface covered by a thin film of condensed argon at small scattering angles (includi ng the case of specular reflection) were examined. Depending on the de nsity of the film new effects such as a splitting or shifting df the g old quasi-single-scattering peak are observed. It is postulated that t hese effects are connected with multiple scattering of projectiles ins ide the adsorbed film. Multiple scattering directs the ions to the det ector after single scattering from the substrate atoms over the angles larger or smaller than the detection angle. At a certain density of a dsorbed film only large-angle substrate scattering occurs. This phenom enon is manifested experimentally by a shift of the gold quasi-single- scattering peak.