Electron-impact ionization of highly charged hydrogenic atomic ions

Electron-impact-ionization cross sections are calculated for hydrogenic ions with nuclear charge between 26 and 92, for incident electron energies up to 8 times the ionization energy, by a relativistic distorted-wave method. The results demonstrate the increasing importance of relativistic effects with Z and with incident electron energy, particularly for 1s ionization. The effects of including magnetic and retardation interactions as Z increases are also studied. Results are compared with scaled K-shell ionization measurements for ⁴⁷Ag and ⁷⁹Au.