Positron and electron-impact multiple-ionization

Abstract

We present positron-impact multiple (single to quintuple) and total ionization cross sections of Ne, Ar, Kr, and Xe, covering an extended energy range from 50 eV to 7 keV. We improve on previous calculations of the ionization thresholds by adding the mean kinetic energy transferred to the target electrons. In this way the thresholds compare rather well with the experimental appearance energies for the different k-fold ionization cross sections. Present results include not only the novel energy threshold at low energies but also the post-collisional contribution at high energies. We performed a quite complete particle–antiparticle comparison by including our positron-impact results, new calculations for electron-impact ionization including the threshold correction, and a detailed compilation of experimental data. Present positron-impact multiple ionization cross sections are the first ones in such an extended energy region.

Impact parameter moments for ionization of Ne, Ar, Kr, and Xe by protons, considering different initial states and impact energies

“…These values have already been tested in total [27] and differential [28] ionization cross sections. Also the probabilities as function of the impact parameter have been employed in multiple ionization calculations [9,12,13,30] with good agreement with the experimental data, even for sextuple ionization of Kr (Xe), where L-shell (M-shell) contribution is decisive.…”

“…Different approaches have been employed over the years, from the basic first Born approximation, to distorted wave methods, numerical solution of the Schrödinger equation or collective response models [6][7][8][9][10][11]. Moreover, in very recent works, the ionization probabilities by proton and antiproton impact have been the seeds to obtain multiple ionization cross sections of rare gases by electron and positron impact, with reasonably good results [12,13]. It is worth to note that multiple ionization cross sections are highly dependent on the inner-shell ionization probabilities, which contribute to the final values through Auger-type processes [8,12].…”

Generalized binary-encounter-Bethe model for electron impact ionization of atoms

“…The majority of multiply charged ions are formed through autoionzation following a single ionization. This process has been studied both experimentally and theoretically, providing detailed information of the different channels contributing to each final charge state [51,52]. In the previous work, Kim et al [17] provided a rough approximation to predict the major contribution of direct single ionization and ionizationautoionization:…”

Tables of experimental branching ratios of Auger-type post collisional ionization of rare gases

“…In tables 1, 2 and 3 we display the branching ratios used in this work for PCI of 0-6 electrons and all the shells of Ne, Ar, Kr and Xe. These values have already been employed with good results in previous calculations of multiple ionization of rare gases by protons, antiprotons and different positive ions [3,4,6,7,8,9,10,11]. A detailed discussion on the experimental branching ratios and the comparison of the different data available in the literature is included in [3].…”

“…This rearrangement gives rise to P P CI (n) , the probabilities of exactly n emitted electrons, part of them in direct ionization and part in PCI. This formalism has already been employed with good results in previous calculations of multiple ionization including direct and post-collsional contributions [3,4,6,7,8,9,10,11].…”