Many-body theory of the neutralization of strontium ions on gold surfaces

摘要

Motivated by experimental evidence for mixed-valence correlations affectingthe neutralization of strontium ions on gold surfaces we set up anAnderson-Newns model for the Sr:Au system and calculate the neutralizationprobability $\alpha$ as a function of temperature. We employ quantum-kineticequations for the projectile Green functions in the finite$-U$ non-crossingapproximation. Our results for $\alpha$ agree reasonably well with theexperimental data as far as the overall order of magnitude is concerned showingin particular the correlation-induced enhancement of $\alpha$. Theexperimentally found non-monotonous temperature dependence, however, could notbe reproduced. Instead of an initially increasing and then decreasing $\alpha$we find over the whole temperature range only a weak negative temperaturedependence. It arises however clearly from a mixed-valence resonance in theprojectile's spectral density and thus supports qualitatively theinterpretation of the experimental data in terms of a mixed-valence scenario.