Ratio of Cross Sections for Double to Single Ionization of He by 85–400 eV Photons

Abstract

The ratio of double to single ionization of He by 85--400 eV photons has been measured using cold target recoil ion momentum spectroscopy. This technique allows the elimination of all possible systematic errors discussed so far in the literature on this subject. We find the ratio in this energy range to be about 25% lower than previously assumed.