Photoionization of Xe4+ to Xe7+ ions was studied by combining an electron cyclotron resonance ion source with synchrotron radiation. Multiconfiguration Dirac-Fock calculations were performed to interpret the data. Many autoionization lines were measured and identified, resulting from excitation of a 4d electron into nf and np orbitals followed by Auger decay of the excited states. Continuum photoionization is negligible for the higher members of the isonuclear series.

In this paper, we present the first absolute measurements for photoionization of multiply charged oxygen ions: O 2+ and O 3+ in the ground state and in several metastable states, as well as relative data for O 4+. Multiconfiguration Dirac-Fock and relativistic R-matrix calculations were performed and are tested here by comparison with experimental results. Our experimental and new theoretical results are also compared with the earlier theoretical data obtained in the R-matrix approximation to calculate photoionization cross sections over part of the isonuclear series of multiply charged oxygen ions.