Spectroscopy and Ground-State Transfer of Ultracold Bosonic $^{39}$K$^{133}$Cs Molecules

Abstract: We report on the creation of ultracold samples of $^{39}$K$^{133}$Cs molecules in their rovibrational ground state. By investigating potentially suitable excited states using one- and two-photon spectroscopy, we have identified a pathway to the ground state via an exceptionally narrow intermediate state. Using Stimulated Raman Adiabatic Passage (STIRAP), we create trapped samples of up to 3500 molecules at temperatures of 1 $\mu$K with one-way efficiencies of 71%. The lifetime of these samples is limited by a universal-rate two-body loss process, which could shed new light on similar loss mechanisms in other molecular species. Our results are a step towards establishing an alternative platform for the study of bosonic and fermionic quantum matter with strong dipolar interactions.