Direct and indirect ionization of Mg+by energy-resolved electrons

Absolute cross sections for electron impact ionization of Mg + have been measured between threshold and 70 eV. The electrons had a near-Gaussian energy profile with a width (FWHM) of 170 meV and their energy was defined to within 40 meV. Considerable structure due to indirect ionization was revealed, and from comparisons with calculations by Tayal and others, it can be identified as excitation-autoionization and resonant-excitation-double-autoionization. The measurements confirm the existence of several of the resonances seen by Muller et al. (1988-90) but there are some differences between the two experimental results.