Formation of ultracold weakly bound dimers of bosonic 23Na39K

Abstract

We create weakly bound bosonic 23 Na 39 K molecules in a mixture of ultracold 23 Na and 39 K. The creation is done in the vicinity of a so far undetected Feshbach resonance at about 196 G which we identify in this work by atom-loss spectroscopy. We investigate the involved molecular state by performing destructive radio frequency binding energy measurements. For the constructive molecule creation we use radio frequency pulses with which we assemble up to 6000 molecules. We analyze the molecule creation efficiency as a function of the radio frequency pulse duration and the atom number ratio between 23 Na and 39 K. We find an overall optimal efficiency of 6 % referring to the 39 K atom number. The measured lifetime of the molecules in the bath of trapped atoms is about 0.3 ms.

Ultracold Gas of Bosonic Na23K39 Ground-State Mo

“…For heteronuclear bialkali molecules there are ten different molecular species available: LiNa, LiK, LiRb, LiCs, NaK, NaRb, NaCs, KRb, KCs and RbCs, all composed from the 5 different stable alkali metal atomic species; see Fig. 1.1, namely 6,7 Li, 23 Na, 39,40,41 K, 85,87 Rb and 133 Cs. Due to the different isotopes for the alkali metal atoms, some molecules have several isotopologues, which add up to in total 31 different heteronuclear molecules.…”

“…Due to the different isotopes for the alkali metal atoms, some molecules have several isotopologues, which add up to in total 31 different heteronuclear molecules. In recent years just a handful of different ground-state molecules have been created, which are the fermionic 40 K 87 Rb [49], 23 Na 40 K [50] and 6 Li 23 Na [51] and the bosonic 87 Rb 133 Cs [52,53] and 23 Na 87 Rb [54]. These molecules feature unique properties, such as their high electric dipole moments, chemical (in)stability and collision properties.…”

“…On top of that, the basis for any molecule assembly is a dual-species quantum gas apparatus which is by itself a technical and operational expense. The assembly process for polar ground-state molecules follows the pathway originally shown for the first time at JILA for fermionic 40 K 87 Rb molecules [49]. It consists of two major parts, namely the creation of weakly bound molecules (commonly known as Feshbach molecules) [12]; see Fig.…”

“…Later, more findings have been reported by Klempt et al (2008) [75] and [76] for bulk systems. Following these pioneering approaches, other atomic species combinations have been investigated: 6 Li 40 K (2010) [77], 23 Na 40 K (2012) [78], 6 Li 23 Na (2012) [79], 87 Rb 133 Cs (2013) [80], 23 Na 87 Rb (2015) [81]. From all of these weakly bound molecules, except for 6 Li 40 K, also ground-state molecules have been created by using STIRAP.…”

“…Ground-state molecule In this picture, an overview of the bialkali groundstate molecule assembly process from an ultracold atomic mixture is shown, orientated along the molecular potential energy curves. The entire process is analog to the original one for the 40 K 87 Rb molecules [49]. The essential steps (0 th -3 rd ) are labeled according to the succession of this thesis.…”