Abstract
The positive charge fraction resulting from charge exchange during the interaction of and ions on the Ag(110) and Cu(110) metal surfaces has been measured for different energies and incident azimuthal angles of the projectiles. Surprisingly, although metallic Cu and Ag are well described by the free-electron model, the positive charge fraction has been observed to vary significantly according to the azimuthal angle of incidence, for projectile energies lower than and incidence angle below 5° with respect to the surface (grazing scattering conditions), and specifically around the low-index [001] and directions. A detailed analysis of trajectory calculations for the system allows one to distinguish between different types of trajectories (on tops, zigzags, and in rows), the relative importance of which varies rapidly with azimuthal angle. We obtain a good correlation between the observed azimuthal variation of the charge fraction and the mean value of the electronic density encountered by the projectile in the vicinity of the first atomic layers. We show that this short-range effect can be reflected on the observed variation of the charge fraction through the charge image effect on the trajectories. This effect is shown to be very sensitive to the electronic corrugation of the surface which is known to be low for Cu and Ag. Azimuthal experimental measurements thus appear to be a tool to characterize such low corrugations.
3 More- Received 19 January 2007
DOI:https://doi.org/10.1103/PhysRevB.76.045432
©2007 American Physical Society