We investigate the effect of hyperfine interactions on ultracold molecular collisions in magnetic fields, using ^{24}Mg(^1S) + ^{14}NH(^3Sigma^-) as a prototype system. We explore the energy and magnetic field dependence of the cross sections, comparing the results with previous calculations that neglected hyperfine interactions (Phys. Rev. Lett. 103, 183201 (2009)). The main effect of hyperfine interactions for spin relaxation cross sections is that the kinetic energy release of the dominant outgoing channels does not reduce to zero at low fields. This results in reduced centrifugal suppression on the cross sections and increased inelastic cross sections at low energy and low field. We also analyze state-to-state cross sections, for various initial states, and show that hyperfine interactions introduce additional mechanisms for spin relaxation. In particular, there are hyperfine-mediated collisions to outgoing channels that are not centrifugally suppressed. However, for Mg+NH these unsuppressed channels make only small contributions to the total cross sections. We consider the implications of our results for sympathetic cooling of NH by Mg and conclude that the ratio of elastic to inelastic cross sections remains high enough for sympathetic cooling to proceed.
Ultracold molecular collisions in magnetic fields: Efficient incorporation of hyperfine structure in the total rotational angular momentum representation
Quantum spin state selectivity and magnetic tuning of ultracold chemical reactions of triplet alkali-metal dimers with alkali-metal atoms
我们证明，它是可能有效地控制超冷化学反应的碱金属原子碰撞开壳碱金属二聚体在其亚稳三重态通过选择内部超精细和振转状态的反应物，以及通过诱导磁费什巴赫共振与外部磁场。我们基于耦合通道统计计算，包括超精细接触和磁场诱导塞曼相互作用的超精细分辨基态钠和三重态NaLi（$^3Σ^+$）产生单线态Na $_2$（$^1Σ^+_g$）和Li原子的超冷化学反应的影响，这些结论。我们发现反应速率对反应物的初始超精细态很敏感。与未极化的反应物相比，完全自旋极化的无旋转NaLi（a $^3Σ^+, v = 0, N = 0$）分子的高自旋态与完全自旋极化的Na的化学反应被抑制10-100倍。我们解释这些发现内的绝热状态模型，该模型将反应作为一个序列的非绝热过渡之间的初始非反应性高自旋状态和最终的低自旋状态的反应复合物。此外，我们表明，磁费什巴赫共振可以类似地改变反应速率系数的几个数量级。这些共振中的一些是由于共振三聚体束缚态解离成NaLi的$N=2$旋转态（一种$^3Σ^+, v = 0$），因此将存在于没有超精细相互作用的系统中。
Ultracold Dipolar Gas of Fermionic $^{23}$Na$^{40}$K Molecules in their Absolute Ground State
我们报告创建一个超冷偶极气体的费米子$^{23}$ Na $^{40}$ K分子在其绝对振转和超精细基态。从弱结合Feshbach分子，我们证明了超精细分辨双光子转移到单重态${\rm X}^1Σ^+ |v{=}0,J{=}0\rangle$基态，相干桥接的结合能差为0.65 eV通过受激快速绝热通道。自旋极化，近量子简并分子气体显示寿命超过2.5秒，突出了NaK对两体化学反应的稳定性。施加均匀电场以诱导高达0.8德拜的偶极矩。随着这些进展，对$^{23}$ Na $^{40}$ K分子的强偶极费米气体的多体物理探索已进入实验阶段。
Feshbach-optimized photoassociation of ultracold $^6$Li$^{87}$Rb molecules with short pulses
本文研究了在磁费什巴赫共振附近短脉冲作用下，基态$^6$ Li $^{87}$ Rb分子通过$\mathrm{B}^1Π$电子态的双色光缔合.施加近共振磁场以混合初始波函数的超精细单重态和三重态分量并增强光缔合速率，然后通过第二脉冲将群体转移到基态。我们表明，产生的分子的绝对数量的增加高达三个数量级是可以实现的深绑定的振动水平。这种技术可以推广到具有可接近的磁费什巴赫共振的其他分子。
