Laser cooling of CH molecule:Insights from ab initio study

• 来源期刊: 中国物理B（英文版）
• 关键词: spectroscopic constants transition diople moments Franck–Condon factors laser cooling
• 年，卷（期）: 2018,（10）
• 页码范围: 183-190
• 页数: 8页
• 语种: 英文
• DOI: 10.1088/1674-1056/27/10/103101

摘要

The feasibility of laser cooling a CH molecule is investigated theoretically by employing the ab initio method. The potential energy curves for the fiveΛ–S states and eight?states of CH are determined by the multi-reference configuration interaction with the Davidson corrections (MRCI+Q) level of theory. The results agree well with the available experimental data and other theoretical values. Also, the permanent dipole moments and transition dipole moments of the CH molecule are calculated at the multi-reference configuration interaction (MRCI) level. We find highly diagonally distributed Franck–Condon factors ( f00=0.9950 and 0.9998) and branching ratios (R00=0.983 and 0.993) for the A2?→X2Πand C2Σ+→X2Π transitions. Moreover, the values of suitable radiative lifetime τ of the A2? and C2Σ+ states are evaluated to be 9.64×10?7 s and 2.02×10?7 s, respectively, for rapid laser cooling. A scheme for laser cooling the CH molecule is designed. In the proposed cooling scheme, three wavelengths for A2?→X2Πand C2Σ+→X2Πtransitions are used, and the main pump lasers areλ00=430.86 nm and 313.45 nm, respectively. The feasibility of laser cooling the CH molecules is demonstrated for each of these schemes, and this study offers a theoretical basis for experimental research into preparation of cold CH molecules.