Xia Wensha, Ma Haitao, Bian Wensheng
Beijing National Laboratory for Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.
J Chem Phys. 2021 Nov 28;155(20):204304. doi: 10.1063/5.0072013.
Laser cooling of polyatomic molecules to the ultracold regime may enable some new science and technology applications; however, the related study is still at its very early stage. Here, by means of accurate ab initio and dynamical calculations, we identify two new candidate tetratomic molecules that are suitable for laser cooling and demonstrate the feasibility and advantage of two laser cooling schemes that are able to produce ultracold CaCCH and SrCCH molecules. The internally contracted multiconfiguration reference configuration interaction method is applied, and excellent agreement is achieved between the computed and experimental spectroscopic data. We find that the XΣ →AΠ transitions for both candidates feature diagonal Franck-Condon factors, short radiative lifetimes, and no interference from intermediate electronic states. In addition, the crossings with higher electronic states do not interfere. We further construct feasible laser cooling schemes for CaCCH and SrCCH, each of which allows scattering 10 photons for direct laser cooling. The estimated Doppler temperatures for both CaCCH and SrCCH are on the order of μK.
将多原子分子激光冷却至超冷状态可能会带来一些新的科学技术应用；然而，相关研究仍处于非常早期的阶段。在此，通过精确的从头算和动力学计算，我们识别出两种适用于激光冷却的新型候选四原子分子，并证明了两种能够产生超冷CaCCH和SrCCH分子的激光冷却方案的可行性和优势。应用了内部收缩多组态参考组态相互作用方法，计算得到的光谱数据与实验数据取得了极好的一致性。我们发现，两种候选分子的XΣ→AΠ跃迁均具有对角弗兰克-康登因子、较短的辐射寿命，且不受中间电子态的干扰。此外，与较高电子态的交叉也不会产生干扰。我们进一步为CaCCH和SrCCH构建了可行的激光冷却方案，每种方案都允许散射10个光子以进行直接激光冷却。CaCCH和SrCCH的估计多普勒温度均在微开尔文量级。
