FTIR spectrum of vinyl fluoride near 3.6 mu m: rovibrational analysis of the nu(4)+nu(7) band and modelling Coriolis resonances in a seven-level polyad

摘要

The Fourier transform infrared (FTIR) spectrum of vinyl fluoride, H2C=CHF, has been widely investigated in the region of the nu(4) + nu(7) combination band around 2800 cm(-1) at a resolution of 0.005 cm(-1). This vibration of A' symmetry gives rise to an a/b-hybrid band with a predominant a-type component. The rovibrational structure is strongly perturbed and the analysis has been rather complicated since this combination band is involved at least in a seven-level interacting polyad, including the nu(8)+2 nu(10), 2 nu(8)+nu(10), 2 nu(7)+nu(9), nu(7)+nu(8)+nu(12), nu(5)+nu(9)+nu(10) and nu(7)+nu(10)+nu(12) vibrational states. The study has been further complicated by the absence of transitions coming from the perturbers that were considered as dark states. The spectral analysis resulted in the identification of 936 transitions with J '' = 46 and K-a '' = 11, all belonging to the a-type component. Most of the assigned data have been fitted using the Watson's A-reduction Hamiltonian in the Ir representation and proper Coriolis perturbation operators. The model employed includes seven different resonances within a complex polyad resonant system and a set of spectroscopic constants for the nu(4)+nu(7) combination band, for the dark states, and Coriolis coupling coefficients have been determined.