Preparation of a quantum degenerate mixture of 23Na 40K molecules and 40K atoms

We report on the preparation of a quantum degenerate mixture of 23Na 40K molecules and 40K atoms. A deeply degenerate atomic mixture of 23Na and 40K atoms with a large number ratio (NF/NB approximate to 6) is prepared in a large-volume optical dipole trap. About 3.0 x 104 23Na 40K ground-state molecules are created through mag-netoassociation 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.