Photoionization of Rb$^2$ ions in the valence energy region 37-44 eV

Absolute photoionization cross sections for the Rb2+ ion were recently measured at high resolution over the energy range 37.31–44.08 eV, with autoionizing Rydberg resonance series identified, using the photon-ion merged-beam setup at the Advanced Light Source (als) in Berkeley (Macaluso D A et al 2016 J. Phys. B: At. Mol. Opt. Phys. 49, 235002; 2017 50, 119501). Detailed photon-energy scans taken at 13.5 $\pm$ 2.5 meV bandwidth illustrated multiple Rydberg resonance series associated with the ground and metastable states. Here we present theoretical cross section results obtained using the Dirac–Coulomb R-matrix approximation with a detailed analysis of the resonances. The calculations were performed for the , ground state and the corresponding metastable level. Results from the large-scale calculations are benchmarked against the ALS high-resolution measurements and reproduce the dominant resonance features in the spectra, providing confidence in the theoretical work for astrophysical applications.