DOUBLE PHOTOIONIZATION OF HELIUM AT INTERMEDIATE PHOTON ENERGIES

Double photoionization of helium is considered at the photon energies between several hundred eV and several keV. The double-to-single cross section ratio is calculated as an expansion in inversed powers of ene rgy, shared by the electrons. The final state interaction between the outgoing electrons is taken into account in the lowest order of their Sommerfeld parameter. The relative importance of the energy-dependent contributions caused by interactions in the initial and final states i s analysed. The role of the interactions and correlations in the groun d state is studied. The energy distribution of the outgoing electrons is discussed.