Formation of ultracold weakly bound dimers of bosonic $^{23}\textrm{Na}^{39}\textrm{K}$

TL;DR

This paper reports the creation and characterization of weakly bound bosonic $^{23}$Na$^{39}$K molecules near a new Feshbach resonance, demonstrating molecule assembly efficiency and lifetime in an ultracold mixture.

Contribution

The work identifies a new Feshbach resonance at 196 G and demonstrates the formation of up to 6000 molecules with a 6% efficiency, including measurements of binding energy and molecule lifetime.

Findings

Identified a new Feshbach resonance at 196 G.

Achieved formation of up to 6000 molecules.

Measured molecular lifetime of about 0.3 ms.

Abstract

We create weakly bound bosonic $^{23}\textrm{Na}^{39}\textrm{K}$ molecules in a mixture of ultracold $^{23}\textrm{Na}$ and $^{39}\textrm{K}$. The creation is done in the vicinity of a so far undetected Feshbach resonance at about $196\,\text{G}$ 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 $^{23}\textrm{Na}$ and $^{39}\textrm{K}$. We find an overall optimal efficiency of $6\,\%$ referring to the $^{39}\textrm{K}$ atom number. The measured lifetime of the molecules in the bath of trapped atoms is about $0.3\,\textrm{ms}$.