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Target nuclear charge dependence of double ionization of two-electron ions by MeV protons

The authors have calculated single and double ionization cross sections in the first Born approximation for two-electron ions of varying nuclear charge, ZN. Electron correlation is essential to this process, and the target nuclear charge scaling is used to study this correlation. As ZN is increased the single ionization cross section is found to scale as ZN-4 and the double ionization as ZN-6, in agreement with simple analytical predictions based on a perturbative treatment of the electron-electron interaction.