Angular distribution of electrons following double photoionization

The angular distribution of continuum electrons following double photoionization of helium is calculated using a final-state wavefunction which accounts for Coulomb interactions between all three particles (nucleus and two electrons). Particularly in the case of almost equal energies of the two electrons, strong effects from electron repulsion on the angular distribution are predicted. Selection rules excluding certain momentum configurations are proposed. When only one electron is detected, agreement is obtained with measured values of the asymmetry parameter beta of its distribution.