本實驗的目標是要實現鉀-39 原子的全光學式量子氣體， 我們透過小角度交叉重疊兩道光學陷阱(optical dipole trap,ODT)來增加捕獲的原子數目並限縮原子在軸方向的運 動。使用這個長寬比小於 20 的複合式光學陷阱，可以穩定 補捉 1 ~ 2*106個鉀原子。然後我們使用磁費許巴赫共振技 術去控制原子間的交互作用，並測量了從 20 G 至 560 G 之 間的所有譜線，我們發現許多譜線在理論工作的文獻中有發 表，但目前沒有任何的實驗發表記錄，我們藉由費許巴赫共 振技術的幫助將鉀原子團的溫度降至 10 μk 以下時發現，S 波散射長度與二體彈性碰撞截面積被有效放大，藉由費許巴 赫共振的幫助，通過強制蒸發冷卻，最佳相空間密度提高到 7 *10-3。 ;The goal of this experiment is to realize all-optical 39K Bose-Einstein Condensates (BEC). We improved the trap loading of a near-IR laser by crossing two beams at a small angle for good loading and tighter axial confinement. With this composite trap, we can routinely trap 1 ∼ 2×106 cold 39K atoms and confine them in a potential well with a trap aspect ratio of less than 20. We then used magnetic Feshbach resonance (FR) to control the atomic interaction in the optical trap. The S-wave scattering length is greatly tuned to improve the two-body elastic collision rate in the trap. We scanned the magnetic field from 20 ∼ 560 G and found intra-spin and inter-spin resonances. Several peaks we found were predicted by literature but not experimental reported to our knowledge. With the help of FR, the best phase space density was increased to 7×10−3 by force evaporative cooling.
