The low-lying electronic states and optical schemes for the laser cooling of the BH+ and BH− ions

• Published in: Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy Vol. 182; pp. 130 - 135
• Main Authors: Zhang, Qing-Qing, Yang, Chuan-Lu, Wang, Mei-Shan, Ma, Xiao-Guang, Liu, Wen-Wang
• Format: Journal Article
• Language: English
• Published: England Elsevier B.V 05.07.2017
• Subjects: Laser cooling; Molecule cool; Optical scheme; Radiative lifetimes; Spectroscopic parameters; Laser cooling; Optical scheme; Molecule cool; Radiative lifetimes; Spectroscopic parameters
• ISSN: 1386-1425; 1873-3557
• DOI: 10.1016/j.saa.2017.04.006

The potential energy curves and transition dipole moments for the 12Σ+, 22Σ+, 12Π and 22Π electronic states of the two molecules are calculated using multi-reference configuration interaction and the large basis sets aug-cc-pwCV5Z. Based on the obtained potential energy curves, the rotational and vibrational energy levels of the states are obtained by solving the Schrödinger equation of nuclear motion, and the spectroscopic parameters are then obtained by fitting the energy levels to Dunham series expansions. The spin-orbit coupling effect of the 2Π states for both the BH+ cation and BH− anion are calculated. Highly diagonally distributed Franck-Condon factors are determined for the 12Σ+ (v″=0)↔12Π (v′=0) transition, ƒ00 (BH+)=0.943, while the Franck-Condon factors for the 12Π (v″=0)↔12Σ+ (v′=0) transition is ƒ00 (BH−)=0.942. Moreover, the radiative lifetime of 38.2ns for the excited 12Π state of the BH+ and 91.8ns for the 12Σ+ state of the BH− are obtained, which are short enough for rapid laser cooling. A three-step optical scheme of the laser cooling is constructed for either the BH+ cation or the BH− anion. The rovibrational levels and spectroscopic parameters of the ground and low-lying excited states of BH+ cation and BH− anion are obtained by ab initio calculations and the laser cooling schemes have been constructed with the 12Σ+↔12Π transitions of BH+ cation and BH− anion. The predicted cooling temperatures of BH+ cation and BH− anion are 11.20μK and 0.38μK, respectively. [Display omitted] •Laser cooling schemes are constructed with 12Σ+↔12Π transitions for BH+ and BH−.•BH+ cation and BH− anion are expected to be cool to 11.20μK and 0.38μK.•The potential energy curves of BH+ cation and BH− anion are obtained.•The ro-vibrational energy levels and spectroscopic parameters are determined.