2-COLOR PHOTOASSOCIATION SPECTROSCOPY OF GROUND-STATE RB-2

We determine the energies of twelve vibrational levels lying within 20 GHz of the lowest dissociation limit of Rb-85(2) with two-color photo association spectroscopy of ultracold Rb-85 atoms. The levels lie in a n energy range for which singlet and triplet states are mixed by the h yperfine interaction. We carry out a coupled channels bound state anal ysis of the level energies, and derive accurate values for Rb-85(2) in teraction parameters. The information obtained is sufficient to allow for quantitative calculations of arbitrary Rb ultracold collision prop erties.