Survival of He + ions during grazing scattering from a Cu(1 1 1) surface

Abstract

He + ions and He atoms with keV energies are scattered under a grazing angle of incidence from an atomically flat and clean Cu(1 1 1) surface. From the comparison of measured charge fractions for specularly reflected charged and neutral projectiles we find evidence for the survival of incident ions from neutralization during the complete scattering event. The survival of ions can only be understood, if the neutralization proceeds around the distance of closest approach, i.e. at the jellium edge. Thus neutralization of ions proceeds closer to the surface than derived in most former evaluations of experimental data where response phenomena are approximated by the concept of classical image charge interactions. From the analysis of our data we derive Auger neutralization rates which compare well with recent theoretical work.