Cross sections and rates for direct electron-impact ionization of sodiumlike ions

Cross sections and rate coefficients for the direct electron-impact ionization of sodiumlike ions have been calculated in a distorted-wave Born exchange approximation. For higher charge states the cross section is dominated by inner-shell ionization of the 2p⁶ subshell. Analytic fits to the data allow rapid calculation of cross sections and rate coefficients over a wide range of incident electron energies. The importance of electron-impact excitation to autoionizing states is discussed.