Preparation of a quantum degenerate mixture of Na23K40 molecules and K40 atoms

Abstract

We report on the preparation of a quantum degenerate mixture of $^{23}\mathrm{Na}\phantom{\rule{0.16em}{0ex}}^{40}\mathrm{K}$ molecules and $^{40}\mathrm{K}$ atoms. A deeply degenerate atomic mixture of $^{23}\mathrm{Na}$ and $^{40}\mathrm{K}$ atoms with a large number ratio (${N}_{F}/{N}_{B}\ensuremath{\approx}6$) is prepared in a large-volume optical dipole trap. About $3.0\ifmmode\times\else\texttimes\fi{}{10}^{4}\phantom{\rule{0.16em}{0ex}}^{23}\mathrm{Na}\phantom{\rule{0.16em}{0ex}}^{40}\mathrm{K}$ ground-state molecules are created through magnetoassociation followed by stimulated Raman adiabatic passage. The pure molecular gas is in the moderately degenerate regime. In the atom-molecule mixture, the elastic collisions provide a thermalization mechanism for the molecules. The calculated thermalization time constant is smaller than the lifetime of the molecules in the atom-molecule mixture. This indicates that the molecules may reach thermal equilibrium due to elastic atom-molecule collisions before notable losses take place. In a few tens of milliseconds, the degeneracy of the molecules is maintained. This time interval is long enough for the study of strongly interacting atom-molecule mixtures and the production of ultracold triatomic molecular gases.