Energy-loss measurements for single and multiple ionization of argon by positron impact

Abstract

Experimental data, as a function of projectile energy loss, are presented for single, double and triple ionization of argon by 750 eV positrons. These differential ionization yields are for positrons scattered into a forward cone of angles between 0° and 17° and for energy losses up to 85% of the initial energy. The single ionization data are shown to be in good agreement with distorted wave Born calculations. For the angular range investigated the percentage of double ionization is found to increase rapidly for the first 80 eV of energy loss. The ratio then slowly approaches a constant value that is in good agreement with the ratios of total cross sections for photoionization of the M shell. The present energy-loss data also demonstrate the importance of outer versus inner-shell ionization in the double and triple ionization channels.