Motivated by experimental evidence for a mixed-valence state to occur in theneutralization of strontium ions on gold surfaces we analyze this type ofcharge-transferring atom-surface collision from a many-body theoretical pointof view using quantum-kinetic equations together with a pseudo-particlerepresentation for the electronic configurations of the atomic projectile.Particular attention is paid to the temperature dependence of theneutralization probability which--experimentally--seems to signalmixed-valence-type correlations affecting the charge-transfer between the goldsurface and the strontium projectile. We also investigate the neutralization ofmagnesium ions on a gold surface which shows no evidence for a mixed-valencestate. Whereas for magnesium excellent agreement between theory and experimentcould be obtained, for strontium we could not reproduce the experimental data.Our results indicate mixed-valence correlations to be in principle present, butfor the model mimicking most closely the experimental situation they are notstrong enough to affect the neutralization process quantitatively.
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