Parallel velocity assisted charge transfer: F- ion formation at Al(111) and Ag(110) surfaces

Theoretical results on the F- ion formation in scattering from Al and Ag su rfaces are presented. Negative ion fractions are studied over a wide range of incident energies and scattering angles. Our description of the ion-surf ace charge transfer takes into account the multistate effects originating f rom the 2p(6) closed shell structure of the F- ion. Based on the parameter- free study of the dynamics of resonant charge transfer we find that the par allel velocity effects are quite important down to projectile energies of 0 .5 keV. This is further confirmed by comparison between the present results and available experimental data [S. Ustaze et al., Surf. Sci. 414 (1998) L 938; M. Maazouz et al., Surf. Sci. 409 (1998) 189; S. Ustaze, L. Guillemot, V.A. Esaulov, personal communications]. (C) 1999 Elsevier Science B.V. All rights reserved.