Potential electron emission above the kinetic emission threshold in slow multicharged ion-surface interactions

Traditionally the electron emission arising in the interaction of multicharged ions with metal surfaces is termed kinetic electron emission (KEE) or potential electron emission (PEE) depending on whether the ejected electrons originate from the conversion of kinetic or potential energy of the incident ion. An investigation of the neutralization dynamics of multicharged ion-surface interactions in the energy region above the KE threshold is difficult since both KEE and PEE contribute to the total electron yield. We present measurements of the total electron yield, {gamma}, for N{sup 2+}, N{sup 5+} and N{sup 6+} ions at 20{degrees} incidence on a Au(011) single crystal, in the velocity range 0.25au-0.55au. Characteristic variations in {gamma} are reported as a function of crystal azimuthal orientation which allow the direct separation of KEE and PEE, and allow, for the first time, an investigation of the neutralization dynamics far above the KE threshold. From our analysis we conclude that above-surface neutralization processes are minor contributors to the total electron yield, and that PE in this energy region is due mainly to secondary cascade within the tar bulk.