Electron-impact single-ionization cross-sections for levels ³P₂, ¹D₂, and ¹S₀ of the ground configuration of the Ar²⁺ ion. DI cross-sections are obtained in the potential of the ionizing ion. The single-ionization cross-sections are calculated using the corrected energy levels of the Ar³⁺ ion. Experiment: open circles with error bars – Diserens et al. (1988); open triangles with error bars – Man et al. (1993). See text for details.