Kinetic electron emission in keV ion-surface collisions

Abstract

KeV ions interacting with a solid surface give rise to kinetic electron emission. We will present measured and calculated absolute electron spectra for protons grazingly incident on a single crystal Cu surface at different azimuthal angles of incidence. The total electron emission amounts to approximately 1 electron per incoming ion and consists predominantly of low-energy electrons, with an exponentially decreasing intensity towards higher energies. For these specific incidence conditions, the ions are first neutralized at relatively large distances above the surface, followed by a series of mainly large impact parameter collisions closer to the surface. Recently we have shown that the dominant mechanism for kinetic electron emission arises from the time dependent perturbation of weakly bound localized electrons occurring during each of these collisions. Our calculations for different azimuthal angles of incidence, and therefore for different impact parameter distributions reproduce our measurements quite well. We also show that the contribution of this mechanism to the stopping power of keV ions scattering off a solid surface is considerable.