Multi-ionization of neon, argon, and xenon and their ions by high-energy-electron impact

Abstract

Estimates have been made of the total ionization cross sections for the collision of high-energy electrons with neon, argon, and xenon atoms and all of their ground-state ions. The 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 of Green, Sellin, and Zachor. Both direct continuum ionization and inner-shell excitation followed by Auger transitions were taken into account. Multiple-ionization cross sections were also estimated using experimental data on electron emission following ejection of inner-shell electrons in the various rare-gas atoms and a simplified model of Auger-vacancy cascading in ions. The computed cross-section values were then used in calculations of the cumulative ionization produced by a relativistic electron-ring beam interacting initially with pressure pulses of the various gases. The results obtained, taken together with previous computations for krypton, indicate a progressive increase in the relative importance of Auger processes with increase in $Z$ such that for xenon (and presumably for higher-$Z$ target atoms), Auger ionization dominates the production rates of most of the multicharged ions formed in such a system.