Scaling laws in double photoionization

Abstract

Double-photoionization cross sections are calculated for two-electron targets ${\mathrm{H}}^{\mathrm{\ensuremath{-}}}$, He, ${\mathrm{Li}}^{+}$, and ${\mathrm{O}}^{6+}$ using a correlated and an uncorrelated two-electron continuum wave function (C3 and C2 models, respectively). As the target nuclear charge ${\mathit{Z}}_{\mathit{T}}$ is increased, the double-photoionization cross section is found to scale as ${\mathit{Z}}_{\mathit{T}}^{\mathrm{\ensuremath{-}}4}$ and the electron energy distribution as ${\mathit{Z}}_{\mathit{T}}^{\mathrm{\ensuremath{-}}6}$. 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 ${\mathit{Z}}_{\mathit{T}}^{\mathrm{\ensuremath{-}}2}$, as in the case of proton impact.