Li Donghui, Fayyaz Faiza, Bian Wensheng
Beijing National Laboratory for Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing, China.
School of Chemical Sciences, University of Chinese Academy of Sciences, Beijing, China.
Front Chem. 2024 Aug 20;12:1460224. doi: 10.3389/fchem.2024.1460224. eCollection 2024.
By means of highly accurate and dynamical calculations, we identify a suitable laser cooling candidate that contains a transition metal element, namely zinc monohydride (ZnH). The internally contracted multireference configuration interaction method is employed to compute the five lowest-lying Λ-S states of ZnH with the spin-orbit coupling effects included, and very good agreement is obtained between our calculated and experimental spectroscopic data. Our findings show that the position of crossing point of the AΠ and BΣ states of ZnH is above the ' = 2 vibrational level of the AΠ state indicating that the crossings with higher electronic states will have no effect on laser cooling. Hence, we construct a feasible laser-cooling scheme for ZnH using five lasers based on the AΠ → XΣ transition, which features a large vibrational branching ratio (0.8458), a large number of scattered photons (9.8 × 10) and an extremely short radiative lifetime (64 ns). The present work demonstrates the importance of electronic state crossings and spin-orbit couplings in the study of molecular laser cooling.
通过高精度的动态计算，我们确定了一种合适的激光冷却候选物，它含有一种过渡金属元素，即氢化锌（ZnH）。采用内收缩多参考组态相互作用方法，计算了包含自旋轨道耦合效应的ZnH的五个最低Λ-S态，计算得到的光谱数据与实验数据吻合得很好。我们的研究结果表明，ZnH的AΠ态和BΣ态的交叉点位置高于AΠ态的' = 2振动态，这表明与更高电子态的交叉对激光冷却没有影响。因此，我们基于AΠ → XΣ跃迁，用五束激光为ZnH构建了一种可行的激光冷却方案，该方案具有大的振动分支比（0.8458）、大量的散射光子（9.8 × 10）和极短的辐射寿命（64 ns）。目前的工作证明了电子态交叉和自旋轨道耦合在分子激光冷却研究中的重要性。
