Microwave Studies of Ultracold NaCs Ground State Molecules

We report on microwave studies on sodium-cesium (NaCs) molecules in their rovibrational ground state. We perform microwave spectroscopy and identify transitions to the first rotationally excited state. The coupling between rotational motion and hyperfine angular momentum is weak in NaCs, leading to a clean rotational structure. We also observe exceptionally strong Rabi coupling, making NaCs an attractive candidate for microwave shielding against collisional losses. This may allow for direct evaporation of NaCs molecules and provide a path to a Bose-Einstein condensate of dipolar ground state molecules.