Electronic excitation and charge exchange in low-energy He+ scattering from solid surfaces

The spectral peak of He+ scattered from solid surfaces usually appears at an energy position smaller than that for elastic binary collisions and is sometimes accompanied by remarkable loss peaks. This is due to 1. inelastic electron exchange between He+ and solid surfaces or 2. excitation of surface valence electrons. The mechanism of the electronic transition which leads to inelastic ion scattering is discussed on the basis of experimental results in the low-energy region (10-1000 eV). The ion neutralization mediated by the molecular state during collision is also discussed. (orig.)