Ionization of argon by electron impact

The ionization efficiency curves for Ar+ and Ar2+ have been measured for electron energies from threshold to 300 eV. Structure in the Ar+ curve has been confirmed and arguments and evidence are put forward to support the view that this structure is due to production of the ion via various channels (in particular the autoionization channels) rather than to ``competition'' between the Ar+ and Ar2+ channels as has been suggested recently.