美国麻省理工学院Juliana J. Park研究小组报道了三态基态分子碰撞中的Feshbach共振。相关论文于2023年2月1日发表于国际顶尖学术期刊《自然》杂志上。

课题组人员报道了一个非常明显和狭窄的(25mG) Feshbach共振在两个三态基态NaLi分子之间的碰撞。这种分子Feshbach共振有两个特殊的特征。首先，由于化学反应性强，碰撞损失率比背景损失率提高了两个数量级以上，背景损失率在p波普遍值处饱和。第二，共振位于两个开放通道几乎简并的磁场中。这意味着中间复合体主要衰变到第二开放通道。

该课题组研究人员使用类似于Fabry-Pérot腔的耦合模式模型来描述谐振损耗特征。他们的观察结果为即使在没有反应障碍的系统中也存在长寿命的相干中间配合物提供了强有力的证据，并为化学反应的相干控制开辟了可能性。

据了解，碰撞共振是修改超冷气体相互作用的重要工具，用于在量子模拟中实现以前未知的哈密顿量，用于从原子气体中创造分子和控制化学反应。到目前为止，这种共振已经在原子-原子碰撞，原子-分子碰撞和Feshbach分子之间的碰撞中观察到，这些分子之间的束缚非常弱。对于超冷基态分子是否存在这种共振一直存在争议，因为可能存在高密度的态和/或共振复合体的快速衰减。

附：英文原文

Title: A Feshbach resonance in collisions between triplet ground-state molecules

Author: Park, Juliana J., Lu, Yu-Kun, Jamison, Alan O., Tscherbul, Timur V., Ketterle, Wolfgang

Issue&Volume: 2023-02-01

Abstract: Collisional resonances are important tools that have been used to modify interactions in ultracold gases, for realizing previously unknown Hamiltonians in quantum simulations1, for creating molecules from atomic gases2 and for controlling chemical reactions. So far, such resonances have been observed for atom–atom collisions, atom–molecule collisions3,4,5,6,7 and collisions between Feshbach molecules, which are very weakly bound8,9,10. Whether such resonances exist for ultracold ground-state molecules has been debated owing to the possibly high density of states and/or rapid decay of the resonant complex11,12,13,14,15. Here we report a very pronounced and narrow (25mG) Feshbach resonance in collisions between two triplet ground-state NaLi molecules. This molecular Feshbach resonance has two special characteristics. First, the collisional loss rate is enhanced by more than two orders of magnitude above the background loss rate, which is saturated at the p-wave universal value, owing to strong chemical reactivity. Second, the resonance is located at a magnetic field where two open channels become nearly degenerate. This implies that the intermediate complex predominantly decays to the second open channel. We describe the resonant loss feature using a model with coupled modes that is analogous to a Fabry–Pérot cavity. Our observations provide strong evidence for the existence of long-lived coherent intermediate complexes even in systems without reaction barriers and open up the possibility of coherent control of chemical reactions.

DOI: 10.1038/s41586-022-05635-8

Source: https://www.nature.com/articles/s41586-022-05635-8