Creation of an Ultracold Gas of Ground-State Dipolar 23Na87Rb Molecules

We report the successful production of an ultracold sample of absolute ground-state (NaRb)-Na-23-Rb-87 molecules. Starting from weakly bound Feshbach molecules formed via magnetoassociation, the lowest rovibrational and hyperfine level of the electronic ground state is populated following a high-efficiency and high-resolution two-photon Raman process. The high-purity absolute ground-state samples have up to 8000 molecules and densities of over 10(11) cm(-3). By measuring the Stark shifts induced by external electric fields, we determined the permanent electric dipole moment of the absolute ground-state (NaRb)-Na-23-Rb-87 and demonstrated the capability of inducing an effective dipole moment over 1 D. Bimolecular reaction between ground-state (NaRb)-Na-23-Rb-87 molecules is endothermic, but we still observed a rather fast decay of the molecular sample. Our results pave the way toward investigation of ultracold molecular collisions in a fully controlled manner and possibly to quantum gases of ultracold bosonic molecules with strong dipolar interactions.