Coincidence measurements of highly charged ions interacting with a clean Au(111) surface

Abstract

We have measured electron number statistics of highly charged ions interacting with a clean single crystal Au(111) surface under various angles of incidence in the range from 45\ifmmode^\circ\else\textdegree\fi{} to almost 0\ifmmode^\circ\else\textdegree\fi{} with respect to the surface. For small angles of incidence (typically about 3\ifmmode^\circ\else\textdegree\fi{}) we have also measured the scattering distribution of the reflected projectiles on a position-sensitive detector in coincidence with the number of emitted electrons. Our results allow a clear separation of above- and below-surface electron emission. By comparison with electron emission yields for very slow projectiles under normal incidence conditions, we are able to determine the number of electrons produced by potential and kinetic emission processes. Simulations of the kinetic electron emission along specific trajectories (e.g., projectiles reflected from ideally flat surface areas as opposed to those entering the crystal at target imperfections) show good agreement with our experimental results.