Theory of metastable deexcitation spectroscopy on simple metals

In this work we investigate the Auger deexcitation process of a slow metastable helium atom (He*) in its triplet state on a Na surface. The electronic properties and the Auger rates of the interacting atom-metal system are calculated self-consistently at any distance of He* from the surface in the framework of the local spin-density approximation using the embedding Green's function method. The energy distribution of the emitted electrons is obtained by integrating the Auger rates along the classical trajectory in the adiabatic approximation. The analysis of the spin-resolved local density of states shows that the excited atomic states broaden into resonances already at large atom-surface distances. The calculated atom deexcitation rates are in good agreement with experimental results.