Double K-shell photoionization of atomic beryllium

Double photoionization of the core 1s electrons in atomic beryllium is theoretically studied using a hybrid approach that combines orbital and grid-based representations of the Hamiltonian. The 1S ground state and 1P final state contain a double occupancy of the 2s valence shell in all configurations used to represent the correlated wave function. Triply differential cross sections are evaluated, with particular attention focused on a comparison of the effects of scattering the ejected electrons through the spherically symmetric valence shell with similar cross sections for helium, representing a purely two-electron target with an analogous initial-state configurationWork partially supported by the MICINN projects FIS2010-15127, ACI2008-0777, and CSD 2007-00010; the ERA-Chemistry project PIM2010EEC- 00751; European grants MC-ITN CORINF and MC-RG ATTOTREND; and the European COST Action CM0702. F.L.Y. acknowledges support from Extesp-MICINN Modalidad B. Work at the Lawrence Berkeley National Laboratory was performed under the auspices of the US DOE under Contract No. DE-AC02-05CH11231 and was supported by the US DOE Office of Basic Energy Sciences, Division of Chemical Science