Diode laser spectrum and rovibrational analysis of the nu(10) band of cis-1,2-difluoroethylene

The infrared spectrum of cis-CHF=CHF has been investigated in the v(10) band region between 1100 and 1152 cm(-1), at a resolution of 0.002 cm(-1), employing a tunable diode laser spectrometer. This vibration of symmetry species B-1 yields a strong a-type band, the analysis of which led to the assignment of more than 2000 lines with J less than or equal to 67 and K-a less than or equal to 26. The P- and R-branch spectrum with high J value is dominated by bandheads spaced by 2C and consisting of a series of lines arising from oblate-type near-degeneracy. From a simultaneous fit of the present GSCD, together with a few literature microwave data, a set of ground state constants up to the quartic coefficients has been obtained using Watson's A-reduction Hamiltonian in the I-r representation. A least-squares fit of the assigned transitions provided excited state constants of the v(10) band, which turned out to be free from perturbations.