THE ANGULAR-DISTRIBUTION OF EQUAL-ENERGY ELECTRONS FOLLOWING DOUBLE PHOTOIONIZATION

The triply differential cross section (TDCS) for double photoionizatio n of helium such that both electrons have the same energy is calculate d for total energies of 10 eV and 20 eV above threshold. Excellent agr eement with recent experimental results is obtained using a three-body Coulomb (3C) correlated final-state wavefunction. Rather surprisingly it is shown that an angular distribution calculated with plane waves as the final state, multiplied by a Coulomb correlation factor arising from the normalization of the electron-electron interaction, gives go od agreement with the 3C results and therefore allows the shape of the TDCS to be explained in a simple way. Some comments on a previous tre atment using 'Wannier' theory are given.