Surface-plasmon-assisted electron-capture mechanism in low-energyHe+(1s)−Al(111)collisions

Abstract

We analyze the neutralization of low-energy ${\mathrm{He}}^{+}(1s)$ ions interacting with an Al surface under grazing incidence. First, we calculate transition rates for the surface plasmon-assisted mode of ion neutralization. A comparison of these transition rates with Auger rates recently reported in the literature indicates that the collective process is dominant from large to intermediate ion-surface distances. Inclusion of these transition rates into a set of rate equations relevant to the ${\mathrm{He}}^{+}(1s)/\mathrm{Al}(111)$ interacting system allows us to compute neutralized fractions and angular distributions of the scattered neutral atoms. Comparison of our results with recent experimental data seems to indicate that proper inclusion of both the Auger and collective surface plasmon rates is essential to explain the experimental results. Finally, a phenomenological rate for transitions into the ground state of He was extracted from experimental angular distributions.