Single photoionization cross section measurements of Au$^{\mathrm{+}}$ ions and first determinations of excited state levels in Au$^{\mathrm{2+}}$

Single photoionization cross-section measurements of Au$^{\mathrm{+}}$ ions were performed using synchrotron radiation and the photo-ion, merged-beams technique at the Advanced Light Source at Lawrence Berkeley National Laboratory. Measurements were made at a photon energy resolution of 18 meV from 18.06 to 25.57 eV spanning the $^{\mathrm{1}}$S$_{\mathrm{0}}$ ground state and $^{\mathrm{3}}$D$_{\mathrm{3}}$ metastable state ionization thresholds. Multiple autoionizing resonance series are identified using quantum defect theory. These series identifications were used to make preliminary determinations of low-lying excited state energy levels in the product Au$^{\mathrm{2+}}$ ion, representing the first experimental determination of these levels.