钾-39 费什巴赫共振的大异常位移
Large anomalous shifts of potassium-39 Feshbach resonances
AI总结：
本研究观测到钾-39的33.6 G和39.9 G费什巴赫共振存在达+7.5 G的大异常位移，揭示其源于费什巴赫分子大动态极化率，为相关量子气体研究提供了关键实验数据。
AI中文摘要：
我们报告了对钾-39原子中33.6 G和39.9 G费什巴赫共振位置的大异常位移的观测，该位移可达+7.5 G，实验条件为原子被限制在1063.9 nm光偶极阱（ODT）中，温度最高约35 μK，阱深最高约136 μK。当通过减小ODT的阱深将原子云冷却到更低温度时，位移随阱深成比例减小，并在零阱深处趋近于零。我们表明，观测到的大位移源于钾-39原子入射对与弱束缚费什巴赫分子之间的大交流斯塔克差，而这又源于费什巴赫分子出乎意料的大动态极化率。从33.6 G和39.9 G共振的测量位移中提取的费什巴赫分子的极化率约为两个入射钾-39原子极化率之和的4至7倍，即比弱束缚费什巴赫分子的通常极化率大4至7倍。费什巴赫分子的大极化率归因于1063.9 nm ODT激光的频率与从最低三重态a³Σ⁺ᵤ势的最后振动能级到激发态b³Σ⁺ᵍ势的某个振动能级的分子跃迁频率的近重合。我们研究的其他钾-39费什巴赫共振表现出零或非常小的位移，对应于分子极化率接近两个入射钾-39原子的极化率之和。
英文摘要：
We report the observation of large anomalous shifts, up to +7.5 G, of the positions of the 33.6 G and 39.9 G Feshbach resonances in potassium-39 atoms confined in a 1063.9 nm optical dipole trap (ODT) at temperatures up to around 35 μK and trap depths up to about 136 μK. When the atom cloud is cooled to lower temperatures, by reducing the trap depth of the ODT, the shifts decrease proportionally with trap depth and approach zero at zero depth. We show that the large observed shifts originate from a large differential ac Stark shift between the incoming pair of potassium-39 atoms and the weakly bound Feshbach molecule, which in turn originates from an unexpectedly large dynamic polarizability of the Feshbach molecule. The polarizabilities of the Feshbach molecules extracted from the measured shifts of the 33.6 G and 39.9 G resonances are about four to seven times the sum of the polarizabilities of the two incoming potassium-39 atoms, that is, about four to seven times larger than the usual polarizability of weakly bound Feshbach molecules. The large polarizabilities of the Feshbach molecules are attributed to a near-coincidence between the frequency of the 1063.9 nm ODT laser and the frequency of a molecular transition from the last vibrational level of the lowest triplet a3Σ+u potential to a vibrational level of the excited b3Σ+g potential. Other potassium-39 Feshbach resonances we have studied exhibit a zero or very small shift, corresponding to molecular polarizabilities close to the sum of the polarizabilities of the two incoming potassium-39 atoms.
