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

We report on the creation of ultracold samples of 39K133Cs molecules in their rovibrational groundstate. 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 3500molecules at temperatures of 1 μK with one-way efficiencies of 71%. The lifetime of these samplesis limited by a universal-rate two-body loss process, which could shed new light on similar lossmechanisms in other molecular species. Our results are a step towards establishing an alternativeplatform for the study of bosonic and fermionic quantum matter with strong dipolar interactions.