Multi-Ionization of Krypton and Its Ions by High-Energy Electron Impact

Abstract

Estimates of the total ionization and multi-ionization high-energy-electron collision cross sections have been obtained for krypton and its ground-state ions. The total cross sections were computed within the framework of the Bethe-Born high-energy-approximation theory using the semiclassical projection-operator technique of Hahn and Watson and the independent-particle model for atoms due to Green, Sellin, and Zachor. Both direct continuum ionization and inner-shell excitation followed by Auger ionizing transitions were taken into account. Multiple-ionization cross sections were then estimated using experimental information on electron emission following ejection of inner-shell electrons in neutral krypton and a simplified model of Auger cascading in ions. The results, applied to a calculation of the cumulative ionization produced by a relativistic electron ring beam interacting with a krypton pressure pulse, indicate that Auger processes have a significant influence in speeding up ionization rates in such a system.