An Ultracold Ensemble of NaCs Ground State Molecules

We report on the creation of sodium-cesium (NaCs) molecules in their rovibrational ground state, assembled from ultracold clouds of Na and Cs atoms [1]. We present one- and two-photon studies of electronically excited molecular states. We use one of these states to transfer NaCs Feshbach molecules [2] to the ground state via stimulated Raman adiabatic passage (STIRAP) and observe 70% transfer efficiency. In the ground state, we measure the two-body loss rate, which approaches the unitary limit. In addition, we measure the DC Stark shift of the ground state with fields up to 2.1 kV/cm, corresponding to dipole moments of 2.6 Debye for NaCs.