1ST BORN CALCULATIONS OF DOUBLE IONIZATION OF HELIUM BY BARE-ION PROJECTILES - CONTRIBUTIONS FROM D-ORBITALS

Previous calculations of double ionisation of helium by MeV protons, antiprotons and other bare ions yielded results in good qualitative agreement with experiment, and in particular reproduced the experimentally observed large difference between the double ionisation produced by protons and that produced by antiprotons. But the results for the ratio of the double to single ionisation were uniformly too low by about 35%. The authors report first Born calculations in which single-electron d orbitals have been added to the earlier basis of s and p functions. The single to double ionisation cross section ratio the authors obtain is now in excellent quantitative agreement with the common high-energy limit of that ratio measured for protons, antiprotons, electrons and alpha particles.

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