THE EFFECT OF A BAND-EDGE OF SURFACE ELECTRONIC STATES ON CHARGE-EXCHANGE IN ATOM-SURFACE COLLISIONS

Within the framework of a time-dependent Anderson-Newns model, charge exchange between an atomic particle and a surface with a finite band o f electronic states is considered. Asymptotically exact solutions of t he model for different time dependences of hopping matrix elements bet ween the atomic and band states are derived. It is shown that for a fi nite energy band, the resulting charge state of the atomic particle ca n be a non-monotonic function of its energy only when the time depende nce of the coupling has an adiabatically part. (C) 1997 Elsevier Scien ce B.V.