Coupled-channels analysis of the (51Σu+,51Πu,53Πu,23Δu) complex of electronic states in rubidium dimer

We present a study of the 51Σu+ and 51Πu electronic states in Rb2 strongly coupled with each other and with the surrounding triplet states. Energies of more than 8000 rovibrational levels of the mutually interacting manifold of states were measured by polarization labelling spectroscopy technique. A deperturbation was performed by coupled-channels analysis involving also the 53Πu and 23Δu states and taking into account both spin-orbit and rotational perturbations. Energies of nearly 99% observed levels in two isotopologues 85Rb2 and 85Rb87Rb were reproduced with a standard deviation of 0.08 cm−1, consistent with the experimental accuracy. Potential energy curves of the four involved electronic states and R-dependent perturbation matrix elements were determined and compared with the most recent theoretical predictions, whenever available.