Proton impact double ionization of noble gas atoms

The cross sections for proton impact double ionization of noble gas atoms have been calculated using Gryzinski's semiclassical formula. The calculated cross sections are in good agreement with experimental results. Values of the ratio σ+/σ++ (single ionization cross section/double ionization cross section) have also been calculated for all noble gas atoms. It is found that the calculated variation of σ+/σ++ with incident proton energy agrees well with experimentally observed variation in the case of helium atom.