Local theory of Auger neutralization for slow and compact ions interacting with metal surfaces

We present a theory of Auger neutralization for slow and compact ions scattered off metal surfaces. When an ion is near the surface, we propose a local model in which free-electron-gas quantities are scaled through the local electronic density at the ion position n(z). It is shown that the results of this local model can be joined to the results of a totally surface calculation, valid when the ion is far from the surface. We have calculated Auger neutralization rates and electron emission spectra for ${\mathrm{He}}^{+}$ ions interacting with a jellium surface of ${\mathit{r}}_{\mathit{s}}$=2.67${\mathit{a}}_0$. The effect of the ion potential on the metal-electron wave functions can be incorporated into the model by means of the effective density setup by the tunneling electrons. Its effect is found to be crucial when comparing our results with available experimental data for ${\mathrm{He}}^{+}$ scattered off Cu surfaces. This simple parameter-free theory yields Auger rates and electron emission spectra comparable with calibrated experiments.