Photoionization of positive ions. I. Oxygen

Photoionization cross sections for all subshells occupied in the ground states of neutral oxygen and each positive ion ${\mathrm{O}}^{+n}$ ($n=1-6\mathrm{}$) have been calculated using Hartree-Slater wave functions. The results show that removal of a $2p$ or $2s$ electron has no effect on the $1s$ cross section other than shifting the threshold. The systematics of the cross section as a function of stage of ionization are analyzed, and the limits of applicability of the hydrogenic model are discussed.