Formation of ultracold K 39 Cs 133 Feshbach molecules
Charly Beulenkamp, Krzysztof P. Zamarski, Robert C. Bird +4 more
We report the creation of an ultracold gas of bosonic K 39 Cs 133 molecules. We first demonstrate a cooling strategy relying on sympathetic cooling of Cs 133 to produce an ultracold mixture. From this mixture, weakly bound molecules are formed using a Feshbach resonance at 361.7 G. The molecular gas contains 7.6 ( 10 ) × 10 3 molecules with a lifetime of about 130 ms, limited by two-body decay. We perform Feshbach spectroscopy to observe several new interspecies resonances and characterize the bound state used for magnetoassociation. Finally, we fit the combined results to obtain improved K-Cs interaction potentials. This provides a good starting point for the creation of ultracold samples of ground-state K 39 Cs 133 molecules.
arXiv:2506.16520•Physical Review A•Oct 28, 2025•1 citation