Electrons from Intra- and Interatomic Auger Processes in Low-Energy Collisions of Singly and Doubly Charged Inert Gas Ions with W(110) Surfaces Partially Covered by Alkali Atoms and NaCL Molecules

Abstract

Electron energy spectra from slow He+, He++, and Ar+ ions colliding under grazing incidence with W(110) surfaces are reported. The surface density of states and the surface work function are varied by the exposure of the W(110) surface to alkali atoms and NaCl molecules. For clean W(110) the sequence of electronic transitions during the collision is similar as reported previously for other clean metals: two electron Auger Capture processes dominate both for He+, Ar+ and He++ collisions. For sufficiently large coverages by alkali atoms resonant capture of one or two surface electrons by the projectile ions leads to the formation of core excited states with two electrons occupying outershell orbitals. These states decay by Auger Deexcitation (Penning ionization) and intra-atomic Auger processes (autoionization and autodetachment), respectively.