Time-dependent close-coupling calculations for the double photoionization of He and H2

Photoionization cross sections for both atomic helium and molecular hydrogen are calculated using a time-dependent close-coupling method. The total electronic wavefunction for the two-electron system is expanded in six dimensions, where four dimensions are represented on a radial and angular lattice and a coupled channels expansion is used to represent the other two dimensions. Double photoionization cross sections are obtained for both He and H-2 for a range of photon energies above the complete fragmentation threshold. Comparisons are made with absolute experimental measurements.