Absolute single photoionization cross section measurements of Rb$^{\mathrm{2+}}$ and Rb$^{\mathrm{3+}}$ ions: experiment and theory

Absolute single photoionization cross-section measurements of Rb$^{\mathrm{2+}}$ and Rb$^{\mathrm{3+}}$ ions were performed using synchrotron radiation and the photo-ion, merged-beams technique at the Advanced Light Source at Lawrence Berkeley National Laboratory. Measurements of Rb$^{\mathrm{2+}}$ were made at a photon energy resolution of 13.5 meV from 37.31 to 44.08 eV spanning the $^{\mathrm{2}}$P$_{\mathrm{3/2\thinspace }}$ground state and $^{\mathrm{2}}$P$_{\mathrm{1/2\thinspace }}$metastable state ionization thresholds. Measurements of Rb$^{\mathrm{3+}}$ were made at a photon energy resolution of 30.0 meV from 49.50 to 62.49 eV spanning the $^{\mathrm{3}}$P$_{\mathrm{2}}$ ground state and $^{\mathrm{3}}$P$_{\mathrm{1,0}}$, $^{\mathrm{1}}$D$_{\mathrm{2}}$, and $^{\mathrm{1}}$S$_{\mathrm{0}}$ metastable state ionization thresholds. Multiple autoionizing resonance series arising from both parent ions are identified using quantum defect theory. The measurements are compared to Breit-Pauli R-matrix calculations.