Low-energy ion neutralization at surfaces: Resonant and Auger processes - art. no. 012901

The interaction of He+ with a typical metal surface (Al or Pd) is described , analyzing in detail the different mechanisms that contribute to the neutr alization of the projectile when backscattered from the surface. Auger and resonant neutralization processes are considered and analyzed including a d etailed quantum-mechanical description of the He-metal interaction, for pro jectile energies between 100 eV and 3 keV. We show that the promotion of th e He-is level, due to its interaction with the metal-atom-core orbitals, is the crucial mechanism making resonant processes operative. We find, howeve r, that resonant processes are much more important for Al than for Pd. In A l, both Auger and resonant processes are equally important for neutralizati on of the ion, while for Pd we find that Auger is the dominant mechanism, m aking the He/Pd system the ideal case for which Hagstrum's exponential law appears to be practically valid for all velocities. We also find qualitativ e agreement with experimental data, which we consider a satisfactory result in view;of the fact that our theory is a complex ab initio calculation fre e of adjustable parameters.