Neutralization of Na+-ions in grazing scattering from the surface of thin Al-films

A theoretical study on the formation of the Na I 3s-term in grazing scattering of Na+-ions from the (1 1 1)-surface of an aluminum crystal and a thin film is performed. For the crystal-surface we find quantitative agreement between experimental and theoretical results. For a thin film the quantization of the electronic states in the direction normal to the surface strongly influences the charge-exchange process. The dependence of the neutral fractions in the scattered beam on the projectile velocity is predicted to be clearly different for electron capture from the film and the semi-infinite crystal.