Many-body perturbation theory is applied to calculate double-electron photoionization for neon and argon. Cross sections for the outer-shell $n{p}^2$ and $\mathrm{nsnp}$ pair excitations are included in both the dipole-length and dipole-velocity formulations. Results are in generally good agreement with recent experimental data.

• Received 8 April 1977

DOI:https://doi.org/10.1103/PhysRevA.16.1525