MG-0 AND H- FORMATION AFTER GRAZING ION-SURFACE SCATTERING

The charge exchange of fast (0.2 ≤ ν/ν0 ≤, 1, ν0 = Bohr velocity) Mg+ and H+ ions grazingly scattered (Φin < 1o) off metal surfaces (Al(111), Ni(111)) has been studied. We have investigated the dependence of the neutral charge state fraction of Mg and of H- formation on projectile velocity. The experimental data are successfully interpreted as resonance tunneling between the conduction band of the metal and the two-electron ns21S ground states of Mgo (n = 3) and H- (n= 1), respectively. For a quantitative description the Fermion nature of electrons (i.e., Pauli principle) and the fast motion parallel to the surface (i.e., Galilean transformation) have to be taken into account. In contrast to neutralization of Mg+ ions, H- formation is found to depend strongly on the grazing angle of scattering. This feature is well described by our theoretical calculations. © 1990.