Prospects for the formation of ultracold ground state polar molecules from mixed alkali atom pairs

Photoassociation rates of mixed cold alkali atom pairs and formation rates of cold heteronuclear alkali dimers in their ground state are computed within an approach where the wave functions are calculated exactly, and the laser field is treated as a perturbation. These rates are predicted to have the same magnitude for all heteronuclear species involving either Rb or Cs atoms. Moreover, these rates are found slightly smaller than, or similar to, the same rates for Cs-2 molecules, which is encouraging for future experiments. We studied the specific case of the photoassociation into excited molecular states coupled with spin-orbit interaction, emphasizing the role of the so-called resonant coupling in the formation of stable ultracold molecules with low vibrational levels. The comparison with recent experimental results on RbCs photoassociation and cold molecule formation show their reasonable agreement with our calculations.