Atomic description and velocity effects for surface-plasmon neutralization rates inHe+(1s)/Alsystems

Abstract

In this work we study the effects of both atomic description and ion velocity on the surface-plasmon mediated neutralization rates for low energy ${\mathrm{He}}^{+}(1s)$ ions interacting with Al surfaces. The transition rates appear to have a weak velocity dependence for ion velocities below 0.5 a.u. It is also shown that differences in the atomic description of the final neutral helium atoms are responsible for the strong discrepancies between recently published surface plasmon transition rates and earlier multielectron Auger rates. The relevance of the surface collective response during the ion neutralization is illustrated for intermediate and large ion-surface distances. For the case of grazing incidence, we analyze the velocity effects for the corresponding angular distributions of the final neutral He atoms. Earlier calculations had been performed within the fixed ion approximation. We find that although both the collective neutralization rates and the neutralized fractions depend very weakly on the parallel velocity, its effects on the angular distributions are clearly noticeable.