Chin. Phys. B Vol. 26, No. 2 (2017) 023105MRCI+Q study of the low-lying electronic states of CdFincluding spin orbit coupling ∗Shu-Tao Zhao(赵书涛) 1,† , Bing Yan(闫冰) 2,‡ , Rui Li(李瑞) 3 , Shan Wu(武山) 1 , and Qiu-Ling Wang(王秋玲) 11 School of Physics and Electronic Science, Fuyang Normal University, Fuyang 236037, China2 Jilin Provincial Key Laboratory of Applied Atomic and Molecular Spectroscopy (Jilin University),Institute of Atomic and Molecular Physics, Jilin University, Changchun 130012, China3 Department of Physics, College of Science, Qiqihar University, Qiqihar 161006, China(Received 8 October 2016; revised manuscript received 20 December 2016; published online 10 January 2017)CdF molecule, which plays an important role in a great variety of research f ields, has long been subject to numerousresearchers. Due to the unstable nature and heavy atom Cd containing in the CdF molecule, electronic states of the moleculehave not been well studied. In this paper, high accurate ab initio calculations on the CdF molecule have been performedat the multi-reference conf iguration interaction level including Davidson correction (MRCI+Q). Adiabatic potential en-ergy curves (PECs) of the 14 low-lying Λ–S states correlating with the two lowest dissociation limits Cd( 1 S g )+F( 2 P u ) andCd( 3 P u )+F( 2 P u ) have been constructed. For the bound Λ–S and ? states, the dominant electronic conf igurations and spec-troscopic constants are obtained，and the calculated spectroscopic constants of bound states are consistent with previousexperimental results. The dipole moments (DMs) of2 Σ +and2 Π are determined, and the spin–orbit (SO) matrix elementsbetween each pair of X 2 Σ + , 2 2 Σ + , 1 2 Π, and 2 2 Π are obtained. The results indicate that the sudden changes of DMs andSO matrix elements arise from the variation of the electronic conf igurations around the avoided crossing region. Moreover,the Franck–Condon factors (FCFs), the transition dipole moments (TDMs), and radiative lifetimes of low-lying states-theground state X 2 Σ + are determined. Finally, the transitional properties of 2 2 Π–X 2 Σ + and 2 2 Σ + –X 2 Σ + are studied. Basedon our computed spectroscopic information of CdF, the feasibility and challenge for laser cooling of CdF molecule arediscussed.Keywords: CdF, spin–orbit coupling effect, potential energy curves, spectroscopic constantPACS: 31.50.Df, 31.15.aj, 31.15.ag DOI: 10.1088/1674-1056/26/2/0231051. IntroductionThe halides of group IIB (Zn and Cd) have attractedmuch attention due to their signif icant roles in a numberof research f ields. [1] As the candidates generating chemicallaser, the excited states of the halides of Cd have been exten-sively investigated. [2] In addition, zinc is a signif icant elementfor biological systems and synthetic organic chemistry; andalso is an important kind of transition metals in the humanbody, which is related to nerve disease such as Alzheimer’sdisease. [3,4] Another motivation is to seek the potential candi-date molecules for laser cooling. Because of the similar va-lence electronic structure with the f irst experimentally laser-cooled molecule SrF, [5] the cadmium halides have attracted agrowing theoretical and experimental interest. The informa-tion on electronic structures and transition properties for thehalides of group IIB elements is helpful to reveal the bond-ing nature between group IIB metal and halogen atoms, there-fore much theoretical and experimental effort has been madein previous works. [6–8]The transitional properties of halides of Zn and Cd weremainly focused on 2 2 Σ + –X 2 Σ + and 2 2 Π–X 2 Σ + band systems.Early in 1939, the ultraviolet absorption spectra of ZnF weredetected by Rochester and Olsson, and were assigned to a tran-sition from2 Π excited state. [9]Later, a number of experimen-tal works on the electronic states of halides of Zn were carriedout. Moravec et al. [10] observed anion photoelectron spec-troscopy of ZnF and evaluated the spectroscopic parametersof the ground state X 2 Σ + . Subsequently, the pure rotationalspectrum of the X 2 Σ + state was detected by Flory et al., [11]and the excitation energy of A 2 Π state was measured. In con-trast to those on ZnF, the experimental spectroscopy investi-gations on CdF are less extensively. Two emission bands inCdF, yellow–green and orange bands, were f irstly detected byAsundi et al. [12] Later, Fowler recorded the absorption spec-trum in the wavelength range of 2716.2 ? A–2923.5 ? A, [13] andthis spectrum band was tentatively assigned to 2 2 Σ + –X 2 Σ +transition by Huber et al. [14]On the other hand, a series of theoretical investigations∗ Project supported by the National Natural Science Foundation of China (Grant Nos. 11604052, 11404180, and 11574114 ), the Natural Science Foundation ofHeilongjiang Province, China (Grant No. A2015010), the Natural Science Foundation of Anhui Province, China (Grant No. 1608085MA10), the InternationalScience & Technology Cooperation Program of Anhui Province, China (Grant No. 1403062027), the University Nursing Program for Young Scholars with Cre-ative Talents in Heilongjiang Province, China (Grant No. 2015095), and the Natural Science Foundation of Jilin Province, China (Grant No. 20150101003JC).† Corresponding author. E-mail: zhaoshutao2002@163.com‡ E-mail: yanbing@jlu.edu.cn© 2017 Chinese Physical Society and IOP Publishing Ltd http://iopscience.iop.org/cpb http://cpb.iphy.ac.cn023105-1
