Electron-impact single and multiple ionization of Mg+ ions

Absolute cross sections for single, double and triple electron-impact ionization of Mg+ ions have been measured by employing a crossed-beams experimental set-up. Contributions of indirect resonant processes to the total cross section for single ionization such as resonant-excitation-double-autoionization and resonant-excitation-auto-double-ionization have been observed utilizing a high-resolution energy scan technique with statistical uncertainties as low as 0.04%. The experimental cross sections are compared with results of recent R-matrix calculations showing agreement in the overall features but pronounced differences in the details of indirect ionization contributions. Double ionization was found to be dominated by the direct removal of a 2p-electron with subsequent autoionization. There are also indications of indirect processes in the triple ionization of Mg+ but no clear evidence could be established.