Electron-impact ionization of atomic ions in the Sn and Xe isonuclear sequences

Electron-impact ionization cross-sections for all atomic ions in the Sn and Xe isonuclear sequences are calculated using a semi-relativistic configuration-average distorted-wave method. Contributions to the cross-sections are included from both direct ionization and indirect excitation-autoionization. Branching ratio calculations are carried out for Cu-like Sn21+ and Xe25+ and Na-like Sn39+ and Xe43+ to determine when best to Ignore indirect excitation-autoionization contributions due to radiation damping along the isonuclear sequences. Although experiments exist for Xe through to Xe6+. XeS+, and Xe (43+) the configuration-average distorted-wave results only agree well with the Xe8+ measurements, once metastable states are taken into account and with the Xe 43+ measurements once radiation damping of the excitation-autoionization contribution is accounted for. Temperature-dependent rate coefficients are calculated for each Sn and Xe ionization stage and then put in a collisional-radiative formal that should prove useful in modelling astrophysical and laboratory plasmas. Published by Elsevier B.V.