Multiple ionization of argon, krypton and xenon atoms by positron impact

Cross section ratios sigma 2+ / sigma + for double and sigma 3+ / sigma + for triple relative to single ionization of argon, krypton and xenon atoms by positron impact were measured from threshold up to 1000 eV. All sigma 2+ / sigma + ratios exhibit double peak structures of which the high-energy structure is attributed to inner-shell processes, in agreement with theoretical estimates.