Electron ejection by He+ ion impact at rare-gas films: Energy- and spin-resolved studies

The electron ejection processes operative when He+ ions with energies in the range 10–500 eV impact adsorbed rare-gas layers are examined both by analyzing the energy distribution of electrons ejected from the surface and by use of spin-labeling techniques, specifically the use of electron-spin-polarized He+ ions coupled with measurement of the ejected electron polarization. The data for xenon films indicate that at low ion energies electron ejection is associated primarily with an Auger neutralization process similar to that seen at clean high-work-function metal surfaces. At the higher ion energies, however, kinetic ejection becomes important and provides an increasing contribution to the total electron yield. For krypton films kinetic ejection is the dominant ejection mechanism although a small signal associated with Auger neutralization is also seen. In the case of argon only kinetic ejection occurs.