K-shell photoionization of atomic boron

The direct and conjugate shake-up cross sections for the and transitions are calculated for atomic boron in a close-coupling approximation using the R-matrix method. In the photon energy interval 17 - 45 Ryd we find that the total cross section for these secondary processes represents about 30% of the single inner-shell photoionization cross section. The excitation gives the dominant contribution (80% of the total), while the and excitation contributions are broadly comparable with each other in this energy range. The contribution from the transition is negligible. It is then probable that the 2s shake-off excitation dominates the 2p one, giving rise mostly to terms of the 1s2s2p configuration. Our results suggest that the ionization equilibrium of multiply charged B, C, Na, Mg, Al and Si in a low-density soft-x-ray photoionized plasma will be perturbed strongly by such processes.