Coupled singlet-triplet analysis of two-color cold-atom photoassociation spectra

We describe a method that is well suited to analysis of the bound states of the alkali-metal dimers near their dissociation limit. The method combines inverse perturbation theory, coupled-channel bound-state theory, and the accumulated phase method to treat the short-range part of the molecular potentials. We apply this method to analyze the bound-state energies measured in a two-color photoassociation experiment in an ultracold ${}^{85}\mathrm{Rb}$ gas. This analysis yields information on the interactions between ultracold ${}^{85}\mathrm{Rb}$ atoms that is important to the understanding of ultracold Rb collisions and Bose-Einstein condensation.