Positron and electron-impact multipleionization

Abstract

We present positron-impact multiple (single to quintuple) and total ionization cross sections ofNe, Ar, Kr, and Xe, covering an extended energy range from 50 eV to 7 keV. We improve onprevious calculations of the ionization thresholds by adding the mean kinetic energy transferredto the target electrons. In this way the thresholds compare rather well with the experimentalappearance energies for the different k-fold ionization cross sections. Present results include notonly the novel energy threshold at low energies but also the post-collisional contribution at highenergies. We performed a quite complete particle?antiparticle comparison by including ourpositron-impact results, new calculations for electron-impact ionization including the thresholdcorrection, and a detailed compilation of experimental data. Present positron-impact multipleionization cross sections are the first ones in such an extended energy region.