Total positron-impact ionization and positronium formation from the noble gases

Abstract

Detailed measurements of the total ionization cross-sections for Ne, Ar, Kr and Xe by positron impact are presented in the energy range from threshold up to ~1 keV. From these and other available data, the cross-sections for positronium formation are extracted. Comparison is made with other results where available. Structure in the positronium formation cross-section has been found which appears to be associated with positronium formation in excited states. Upper and lower limits on the contribution from these are estimated.