Two-Color Photoassociation Spectroscopy of Ground StateRb2

Abstract

We determine the energies of twelve vibrational levels lying within 20 GHz of the lowest dissociation limit of ${}^{85}{\mathrm{Rb}}_2$ with two-color photoassociation spectroscopy of ultracold ${}^{85}\mathrm{Rb}$ atoms. The levels lie in an energy range for which singlet and triplet states are mixed by the hyperfine interaction. We carry out a coupled channels bound state analysis of the level energies, and derive accurate values for ${}^{85}{\mathrm{Rb}}_2$ interaction parameters. The information obtained is sufficient to allow for quantitative calculations of arbitrary Rb ultracold collision properties.