Relative single- and double-photoionization cross sections of Mg around the 2p→nl resonances

Using highly monochromatized synchrotron light and the ion time-of-flight method to detect singly and doubly charged magnesium ions, we have measured relative single- and double-photoionization cross sections of Mg from 55 to 58 eV, which includes the region of the 2p→nl inner-shell excitations. The resonances were analyzed using Fano profiles and the resonance positions are compared to previously published data. The quantum defect theory is applied to the resonance energies revealing that the published Mg 2p_1∕2 and 2p_3∕2 thresholds need to be revised. In addition, we have determined the double-to-single photoionization ratio in the 55 to 71 eV region.