Li Donghui, Fu Mingkai, Ma Haitao, Bian Wensheng, Du Zheng, Chen Congmei
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. 2020 Jan 28;8:20. doi: 10.3389/fchem.2020.00020. eCollection 2020.
The feasibility of direct laser cooling of SiH, GeH, SnH, and PbH is investigated and assessed based upon first principles. The internally contracted multi-reference configuration interaction method with the Davidson correction is applied. Very good agreement is obtained between our computed spectroscopic constants and the available experimental data. We find that the locations of crossing point between the BΣ and AΔ states have the tendency of moving downwards from CH to SnH relative to the bottom of the corresponding AΔ potential, which precludes the laser cooling of GeH, SnH, and PbH. By including the spin-orbit coupling effects and on the basis of the transition, we propose a feasible laser cooling scheme for SiH using three lasers with wavelengths varying from 400 to 500 nm, which features a very large vibrational branching ratio (0.9954) and a very short radiative lifetime (575 ns). Moreover, similar studies are extended to carbon monosulfide (CS) with a feasible laser cooling scheme proposed. The importance of electronic state crossing in molecular laser cooling is underscored, and our work suggests useful caveats to the choice of promising candidates for producing ultracold molecules.
基于第一性原理对SiH、GeH、SnH和PbH直接激光冷却的可行性进行了研究和评估。应用了带有戴维森校正的内收缩多参考组态相互作用方法。我们计算得到的光谱常数与现有的实验数据取得了很好的一致性。我们发现，相对于相应AΔ势的底部，BΣ态和AΔ态之间的交叉点位置有从CH到SnH向下移动的趋势，这排除了GeH、SnH和PbH的激光冷却。通过考虑自旋-轨道耦合效应，并基于 跃迁，我们提出了一种使用波长在400至500 nm之间变化的三束激光对SiH进行激光冷却的可行方案，该方案具有非常大的振动分支比（0.9954）和非常短的辐射寿命（575 ns）。此外，类似的研究扩展到了单硫化碳（CS），并提出了可行的激光冷却方案。强调了电子态交叉在分子激光冷却中的重要性，我们的工作为选择产生超冷分子的有前景候选物提供了有用的注意事项。
