Spectroscopy and Ground-State Transfer of Ultracold Bosonic   K 39 133 Cs Molecules

We report the creation of ultracold samples of <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:mrow> <a:mtext> </a:mtext> <a:msup> <a:mrow> <a:mmultiscripts> <a:mrow> <a:mi mathvariant="normal">K</a:mi> </a:mrow> <a:mprescripts/> <a:none/> <a:mrow> <a:mn>39</a:mn> </a:mrow> </a:mmultiscripts> </a:mrow> <a:mrow> <a:mn>133</a:mn> </a:mrow> </a:msup> <a:mi>Cs</a:mi> </a:mrow> </a:math> 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, we create trapped samples of up to 3500 molecules at temperatures of <d:math xmlns:d="http://www.w3.org/1998/Math/MathML" display="inline"> <d:mrow> <d:mn>1</d:mn> <d:mtext> </d:mtext> <d:mtext> </d:mtext> <d:mi mathvariant="normal">μ</d:mi> <d:mi mathvariant="normal">K</d:mi> </d:mrow> </d:math> with one-way efficiencies of 71%. The lifetime of these samples is limited by a near-universal two-body loss process, which could shed new light on similar loss mechanisms in other molecular species. Our results are a step toward establishing an alternative molecular species as a platform for the study of bosonic and fermionic quantum matter with strong dipolar interactions.