Low-energy Na+ neutralization on Al(111) and Cu(110) surfaces at grazing incidence

Jellium model is well known and used to understand the neutralization of alkali-metal ions on metal surfacesbut we find it cannot explain our experiments for the neutralization of 0.4 keV and 0.8 keV Na+ ions on Al(111) and Cu(110) surfaces in grazing incidence. As the exit angle increases neutral fractions on Cu(110) surface decreases first and then increases which is similar to our previous results at large scattering angles. While for the Al (111) surface we observe opposite characteristics. This anomalous bell-shaped feature cannot be explained by the Jellium model. One possible explanation is the inner 2p electron promotion at smaller exit angles this may cause the Na* excited states to be generated and produce excess Na+ ions while the similar electronic excitation process is inefficient for the Cu(110) surface in the present energy range.