Rydberg spectra of singlet metastable states of O2

Updated analyses of several singlet Rydberg states of O2 via spectra involving excitation from the metastable a1?g and b1Σg+ states are presented. The high-quality FT-VUV spectra available from the DESIRS beamline at the SOLEIL synchrotron gives significantly improved spectra compared to previous work. The Rydberg states analysed include 3pπ1Σu+ v?=?0?4, 3pσ1?u v?=?0?2, 3pπ1?u v?=?0?2, 4pπ1Σu+ v?=?0?1, 4pσ1?u v?=?0 and 4pπ1?u v?=?0. This is complemented by high-quality ab initio calculations on the 1Σu+ and 1?u Rydberg states to determine the transition moments providing the first quantitative cross-sections for Rydberg ? b1Σg+ transitions. These are validated against the experimental data. The results suggest the most promising candidate for determining b1Σg+ number density is likely to be the 1?0 band of the 4pπ1Σu+?b1Σg+ transition at 131.3?nm.