Interaction of metastable noble-gas atoms with transition-metal surfaces: Resonance ionization and Auger neutralization

Electron emission due to deexcitation of metastable noble-gas atoms occurs at transition-metal surfaces which are either clean or covered by atomic adsorbates via resonance ionization of the metastable atom and subsequent Auger neutralization. The resulting electron-energy distributions contain information on the local surface density of states. For analysis, the electron-energy distribution is approximated by a self-convolution function. The validity of this approximation is discussed in detail. The deconvolution of the experimental data yields an effective transition density function reflecting the main features of the electronic surface density of states. The deconvolution technique is described in the Appendix. Furthermore, results are presented on the angular distribution of electrons emitted by Auger neutralization as well as on the lowering of the ionization potential of meta- stable and ground-state noble-gas atoms at surfaces which provides information on the distance range where resonance ionization, Auger neutralization, and Auger deexcitation occur.