High-resolution FTIR study of the ν2 fundamental of cis-CHFCHF

Abstract

The high-resolution FTIR spectrum at room temperature of cis-1,2-difluoroethylene has been analyzed in the ν₂ fundamental region from 1670 to 1760 cm⁻¹. This vibration of A₁ symmetry, corresponding to the CC stretching, gives rise to a strong b-type band approximately centered at 1719 cm⁻¹. The rovibrational analysis led to the assignment of many transitions in the P, Q and R branches with J′⩽70, K_a^′⩽30, K_c^′⩽69. From a simultaneous fit of the ground state combination differences coming from the present work and the previously analyzed ν₄ and ν₁₀ fundamentals, together with a few literature microwave data, a set of ground state parameters, including all the quartic and four new sextic centrifugal distortion coefficients, was derived. Using the Watson's A-reduction Hamiltonian in the I^r representation, from the final fit of about 3600 assigned transitions, accurate rovibrational constants for the upper state were obtained with a standard deviation of about 8 × 10⁻⁴ cm⁻¹.