Photoionization of atomic barium including effects of relaxation and polarization

The photoionization cross sections of the 4d¹⁰, 5s², 5p⁶, and 6s² subshells of atomic barium and the angular distribution asymmetry parameters for the 4d¹⁰ and 5p⁶ subshells have been calculated using many-body perturbation theory. Our main purpose is to determine whether relaxation and polarization effects can account for the large difference between recent 4d photoemission experiments and total absorption experiments. Coupling between a number of LS-coupled final-state channels has been included. Relaxation effects have been included by evaluating many-body diagrams and also by calculating excited orbitals in the field of the relaxed ionic core. In the latter case, overlap integrals between initial- and final-state orbitals of the spectator electrons were included. Polarization effects have been included by evaluating many-body diagrams. Results are compared with experiments and other calculations.