Free rotor model or rigid rotor model for CH3F-Ne complex and comparison with other CH3F-rare gas systems
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The assignment of the rovibrational spectra of molecule-Ne complexes is always a challenge to study van der Waals systems, since they usually exhibit behavior intermediate between free rotor and rigid rotor. In this paper, the microwave and infrared spectra of CH3F-Ne, a model system for symmetric-top-atom dimer, were firstly predicted and analyzed based on the four-dimensional ab initio intermolecular potential energy surfaces(PESs), which explicitly incorporate the v 3(C—F) stretch normal model coordinate of the CH3F monomer. Analytic three-dimensional PESs were obtained by least-squares fitting vibrationally averaged interaction energies for v 3(CH3F)=0 and 1 to the Morse/long-range(MLR) potential function for symmetry top impurity with atom model. These PESs fitting to 2340 points have root-mean-square(RMS) deviations of 0.07 cm–1, and require only 167 parameters. Based on the analytical vibrationally averaged PESs, the rovibrational energy levels were calculated by employing Lanczos algorithm, with combined radial discrete variable representation and parity-adapted angular finite basis representation. Based on the wavefunction analysis and comparison of CH3F-Ne with CH3F-He and CH3F-Ar complexes, the bound states were assigned. Spectral parameters for CH3F-Rg(Rg: rare gas, Rg=He, Ne, Ar) complexes were fitted and discussed. Temperature dependent transition intensities for CH3F-Ne were also reported and analyzed. The complete microwave and infrared spectra information for CH3F-Ne made it possible to provide important guidance for future experimental spectroscopic assignments.
KeywordsMorse/long-range model Rovibrational spectrum Symmetry-top molecule CH3F-Ne
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