We present theoretical single to quintuple ionization cross sections for Ne, Ar, Kr and Xe bombarded by H + and He + . Post-collisional contributions due to Auger-like processes are taken into account using recent photoionization data. The present continuum distorted wave-eikonal initial state (CDW-EIS) and first Born approximation results are compared with the experimental data available in the energy range of 50-10 000 keV amu −1 for H + on Ne and Ar, and 50-1000 keV amu −1 for the other cases. In general, the combination of the CDW-EIS with the post-collisional branching ratios describes well the multiple ionization data above 300 keV amu −1 , showing a clear tendency to coalesce with the first Born approximation at high energies. The surprising result of this work is the good performance of the first Born approximation which describes rather well the experimental data of double and triple ionization, even in the intermediate energy range (50-300 keV amu −1 ), where direct ionization is the dominant contribution.

We present a study on multiple ionization of Ne, Ar, Kr and Xe by antiproton, proton and electron impact. Four different aspects are involved in this work. First, the theoretical calculations of ionization probabilities by impact of antiprotons and protons, in an extended energy region (25 keV to 10 MeV), using the continuum distorted-wave eikonal initial state approximation and the first Born approximation. Second, the inclusion of Auger-type post-collisional contributions through experimental photoionization branching ratios. These contributions to multiple ionization are very important in the high-energy region. Third, the comparison with the available experimental data on multiple ionization by protons and antiprotons in the extended energy range, and by electrons for high-impact velocities, where proton, antiproton and electron impact results are expected to converge. It is also the energy region where direct ionization does not explain the experimental results, and the post-collisional ionization is the main contribution to multiple ionization. And fourth, total ionization cross sections are calculated and compared with the antiproton, proton and electron experimental data, showing the importance of Auger-type multiple ionization for heavy targets even at the level of total cross sections. Gross and count cross sections are scrutinized.

This work describes the multiple ionization cross sections of rare gases by electron-impact. We pay special attention to the high energy region (0.1-10 keV) where the direct ionization is a minor contribution and the post-collisional electron emission dominates the final target charge state. We report here electron-impact single to sextuple ionization cross sections and total ionization cross sections including direct and post-collisional processes, even in the total values. We use the continuum distorted wave and the first Born approximations adapted to describe light-particle impact, i.e. energy, mass and trajectory corrections are incorporated, the latter by considering the electron-target potential and by using the Abel transformation. Auger-type post-collisional contributions are included in the multinomial expansion through experimental branching ratios after single ionization events. Tabulations of these experimental branching ratios for all the orbitals of the four targets are included. Present results are compared with the large amount of electron-impact experimental data available. We have obtained a good description of the multiple-ionization measurements at high energies, where the post-collisional ionization dominates. At intermediate energies, our theoretical results show the correct tendency, with the electron-impact ionization cross sections being far below the proton-impact ones.

Pure multiple ionization cross sections of Ne by B 2+ projectiles have been measured in the energy range of 0.75 to 4.0 MeV and calculated using the continuum distorted wave-eikonal initial state approximation. The experiment and calculations show that the ionization cross sections by B 2+ , principally for the production of highly charged recoils, is strongly enhanced when compared to the bare projectile with the same charge state, He 2+ , at the same velocities.

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We have developed a many-electron model for multiple ionization of heavy atoms bombarded by bare ions. It is based on the transport equation for an ion in an inhomogeneous electronic density. Ionization probabilities are obtained by employing the shell-to-shell local plasma approximation with the Levine and Louie dielectric function to take into account the binding energy of each shell. Post-collisional contributions due to Auger-like processes are taken into account by employing recent photoemission data. Results for single-toquadruple ionization of Ne, Ar, Kr and Xe by protons are presented showing a very good agreement with experimental data.

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