Resonant charge transfer in grazing atom-metal surface collisions: Effect of the presence of steps on the surface

The resonant charge transfer process between an atom and a metal surface is studied in the case of a stepped surface. A sudden approximation is introduced to model the effect of steps in the dynamics of the charge transfer process for grazing angle collisions. It is applied to the problem of H- formation by scattering on AI(111) surfaces. The final H- fractions are demonstrated to be very sensitive to the density of steps on the surface. A large difference between the effect of steps up and down is found. The analysis of this phenomenon is performed. The results are compared with the experimental results of Wyputta et al. [Nucl. Instrum. Methods B 58 (1991) 379].