Electron-impact ionization of highly charged lithiumlike ions

We have calculated electron-impact ionization cross sections for Li-like ${\mathrm{Ar}}^{15+}$, ${\mathrm{Fe}}^{23+}$, ${\mathrm{Kr}}^{33+}$, and ${\mathrm{Xe}}^{51+}$ ions for incident electron energies between 3 and 4 times the ionization threshold using the relativistic distorted-wave and the multiconfiguration Dirac-Fock methods. The calculations include direct-ionization, excitation-autoionization and resonant-excitation-double-autoionization processes. There are many narrow resonances due to the excitation of the 1s2s3lnl’ states. The effect of indirect processes persists to very highly charged ions in the isoelectronic sequence.