Double photoionization of excited He-like atoms

Abstract

We have developed a B-spline based technique for evaluatingdouble photoionization rates for He-like atomic systems. Theaccuracy of the approach is tested by comparing the results fromthis code with available theoretical and experimental resultsfor double ionization of the 1s2 and 1s2s 1S states of He.We require significantly more angular momenta to obtainconverged results for 1s2s 1S than for 1s2, which isascribed to the larger spatial extent of the 1s2s 1Swavefunction. By extending the calculations to Li+,Be2+, C4+ and O6+, we show that no obvious1/Z2 scaling law applies to the ratio between double andsingle photoionization of the 1s2s 1S state, in contrast tothe 1s2 1S state.