Time-dependent independent-particle model calculation of multiple capture and ionization processes inp−Ar,p¯−Ar,andHe2+−Arcollisions

Abstract

Previous work on multielectron transitions in proton, antiproton, and ${\mathrm{He}}^{2+}$-ion impact on neon is extended to the case of argon targets for collision energies in the 5--1000 keV/amu range. Global quantities such as net electron loss from the target, net capture, and net ionization are predicted within experimental errors using a spherically symmetric optimized effective target atom potential with dynamical screening effects based on the time-dependent net ionization probability. The inclusion of target response is crucial in order to obtain correct positions and heights for the peaks in the net ionization cross sections. Effects due to cascading following multiple outer-shell excitation are found to be appreciable at energies between 10 and 100 keV/amu, but are overestimated by the statistical model. L-shell vacancy production is reported to affect recoil charge state production at energies above 200 keV/amu for charge states $q>~3.$ At low and intermediate energies, the independent-particle model is shown to overestimate q-fold recoil ion production significantly for $q>~3$ for proton impact signaling the role of electronic correlations for these channels. For antiproton impact the $q=3$ cross section is consistent with the independent-particle model.