Influence of inner-shell electron removal on the multiple ionization of Kr and Xe by protons

Abstract

The multiple ionization of Kr and Xe by protons has been analysed in detail within the independent particle model. The dependence of the multiple ionization cross sections on the values of the ionization probabilities has been investigated for each target subshell and the most relevant pathways for final quadruple to sextuple ionization are identified. The influence of post-collisional ionization probabilities due to Auger-like effects after the removal of one or more inner-shell target electrons has also been considered. It has been observed that, for large final charge states of the target, deep-core ionization plays an important role, due to the increase in the number of ejected electrons arising from post-collisional effects.

Electron-impact multiple ionization of Ne, Ar, Kr and Xe

“…Our CDW-EIS and first Born calculations include all the shells of Ne and Ar, L-M-N shells of Kr and M-N-O shells of Xe. This is important because even though inner-shells may have very small ionization cross sections, their contribution to multiple is important due to cascade Auger processes [36]. We verified that the deeper sub-shells included here (2s of Kr and 3s of Xe) are actually small contributions even in sextuple ionization, and no deeper orbitals are needed.…”

“…In tables 2, 3 and 4 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 MI of rare gases by protons, antiprotons and different positive ions [34][35][36][37][38]62]. A detailed discussion on the experimental branching ratios and the comparison of the different data available in the literature is included in [37].…”

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

“…However, for M-shell ionization the situation is different: we got a clear discrepancy with the ECPSSR results [35] and no experimental data is available. Present M-shell ionization probabilities of Kr have already been employed in multiple ionization calculations with very good agreement with the experimental data [9,30]. In triple and quadruple ionization of Kr at high energies the M-shell ionization plays a mayor role due to single ionization followed by Auger emission of 2 or more electrons.…”

“…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.…”

“…On the other hand, the cross sections for highly ionized targets (i.e. triple ionization of Ar, quintuple ionization of Kr, sextuple ionization of Xe) strongly depend on inner-shell contributions due to Auger cascade processes [12,30].…”