We report a compact experimental setup for producing a quantum degenerate mixture of Bose 23 Na and Fermi 40 K gases. The atoms are collected in dual dark magneto–optical traps (MOT) with species timesharing loading to reduce the light-induced loss, and then further cooled using the gray molasses technique on the D 2 line for 23 Na and D 1 line for 40 K. The microwave evaporation cooling is used to cool 23 Na in | F = 2, m F = 2〉 in an optically plugged magnetic trap, meanwhile, 40 K in | F = 9/2, m F = 9/2〉 is sympathetically cooled. Then the mixture is loaded into a large volume optical dipole trap where 23 Na atoms are immediately transferred to |1,1〉 for further effective cooling to avoid the strong three-body loss between 23 Na atoms in |2,2〉 and 40 K atoms in |9/2,9/2〉. At the end of the evaporation in optical trap, a degenerate Fermi gas of 40 K with 1.9 × 10 5 atoms at T / T F = 0.5 in the |9/2,9/2〉 hyperfine state coexists with a Bose–Einstein condensate (BEC) of 23 Na with 8 × 10 4 atoms in the |1,1〉 hyperfine state at 300 nK. We also can produce the two species mixture with the tunable population imbalance by adjusting the 23 Na magneto–optical trap loading time.
We report on the efficient creation of a sample of 2.2×104 fermionic polar molecules 23Na40K in their rovibrational ground state X1Σ+ |ν = 0, J = 0〉 at 247 nK via an intermediate state of the spin-orbit coupled complex B1Π |ν = 4〉 ∼ c3Σ+ |ν = 25〉. Compared with the intermediate state of the coupled complex B1Π |ν = 12〉 ∼ c3Π+ |ν = 35〉, this intermediate state has the larger Franck-Condon factors for up- and down-leg coupling of stimulated Raman adiabatic passage (STIRAP). We demonstrate this two-photon pathway to the 23Na40K ground state molecules and find that the one-way STIRAP transfer efficiency reaches 75
通过超冷原子的空间自由飞行来获取原子云在动量空间的信息，是超冷原子实验研究中一个重要的探测手段。磁Feshbach共振调控相互作用的超冷原子，需要高偏置磁场下空间自由飞行来获得相互作用能的信息，因此磁场的空间均匀分布对原子自由飞行会产生重要影响。本文对两种绕制的线圈进行了数值模拟，计算了在亥姆霍兹组态下的磁场分布产生，并实验研究了钠原子玻色爱因斯坦凝聚体在不同磁场分布下的自由飞行展开，分析给出了影响自由飞行展开原子密度的磁场线圈参数，为今后设计磁Feshbach共振线圈提供了重要依据。
