L-shell filling of N6+ and O7+ ions from a clean and LiF-covered Au(111) surface

We report on a high-resolution Auger spectroscopy study of the interaction of N6+ and O7+ ions with a clean and a LiF-covered Au(111) target. The elec tron spectra from collisions on Au(111) and LiF-covered Au(111) are distinc tly different. The ones resulting from the interaction with Au(111) covered with one monolayer of LiF resemble spectra taken on bulk LIF, which, in co ntrast to LiF-covered Au(111), is an insulator. On the Au(111) surface and for scattering geometries preventing projectile penetration below the first atomic layer, a more efficient L-shell filling for O7+ than for N6+ ions i s observed. Surprisingly enough, for a single monolayer of LiF on Au the to tal K Auger intensity of nitrogen is nearly 30% larger as compared to the c lean Au(111) target, while for oxygen no enhancement is found. These findin gs demonstrate that, for specific projectile-target systems (e.g., N-LiF), an efficient mechanism that fills the projectile L shell is active well bef ore the projectiles reach the surface, so that KLL electrons are emitted at an early stage of the interaction. [S1050-2947(99)04010-X].