title: Analytical Morse/long-range model potential and predicted infrared and microwave spectra for a symmetric top-atom dimer: a case study of CH₃F-He.
abstract: Four-dimensional ab initio intermolecular potential energy surfaces (PESs) for CH3F-He that explicitly incorporates dependence on the Q3 stretching normal mode of the CH3F molecule and are parametrically dependent on the other averaged intramolecular coordinates have been calculated. Analytical three-dimensional PESs for v3(CH3F) = 0 and 1 are obtained by least-squares fitting the vibrationally averaged potentials to the Morse/Long-Range potential function form. With the 3D PESs, we employ Lanczos algorithm to calculate rovibrational levels of the dimer system. Following some re-assignments, the predicted transition frequencies are in good agreement with experimental microwave data for ortho-CH3F, with the root-mean-square deviation of 0.042 cm(-1). We then provide the first prediction of the infrared and microwave spectra for the para-CH3F-He dimer. The calculated infrared band origin shifts associated with the ν3 fundamental of CH3F are 0.039 and 0.069 cm(-1) for para-CH3F-He and ortho-CH3F-He, respectively.
authors.affiliation: Institute of Theoretical Chemistry, State Key Laboratory of Theoretical and Computational Chemistry, Jilin University, 2519 Jiefang Road, Changchun 130023, People's Republic of China.
authors.forename: Yong-Tao
authors.initials: YT
authors.lastname: Ma
authors.affiliation: Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, USA.
authors.forename: Tao
authors.initials: T
authors.lastname: Zeng
authors.affiliation: Institute of Theoretical Chemistry, State Key Laboratory of Theoretical and Computational Chemistry, Jilin University, 2519 Jiefang Road, Changchun 130023, People's Republic of China.
authors.forename: Hui
authors.initials: H
authors.lastname: Li