SCALING LAWS IN DOUBLE PHOTOIONIZATION

Double-photoionization cross sections are calculated for two-electron targets H-, He, Li+, and O6+ using a correlated and an uncorrelated two-electron continuum wave function (C3 and C2 models, respectively). As the target nuclear charge Z(T) is increased, the double-photoionization cross section is found to scale as Z(T)-4 and the electron energy distribution as Z(T)-6. Conclusions are extracted about the behavior of the cross sections in the high-energy and threshold regions. The ratio of double to single photoionization scales as Z(T)-2, as in the case of proton impact.