High-resolution infrared study of vinyl fluoride in the 750-1050 cm-1 region: Rovibrational analysis and resonances involving the v(8), v(10), and v(11) fundamentals

The FTIR spectra of CH2=CHF have been investigated in the v(8), v(10), and v(11) region between 750 and 1050 cm(-1) at a resolution of about 0.002 cm(-1). The v(8) vibration of symmetry species A' gives rise to an a/b-type hybrid band, while the v(10) and v(11) modes of A" symmetry produce c-type absorptions. Due to the proximity of their band origins, the three vibrations perturb each other by Coriolis and high-order anharmonic resonances. In particular, the interactions between the v(8) and v(10) modes are very strong and widespread with band origins separated by only 1.37 cm(-1). Besides the expected c-type characteristics, the v(10) band shows a very intense pseudo a- type component caused by the strong first-order Coriolis resonances with the v(8) state. Furthermore, the 2"9 " dark state" was found to be involved in the interacting band systems. The spectral analysis resulted in the identification of 3144, 3235, and 3577 transitions of the v(8), v(10), and v(11) vibrations, respectively. Almost all the assigned data were simultaneously fitted using the Watson's A- reduction Hamiltonian in the Ir representation and the perturbation operators. The model employed includes nine types of resonances within the tetrad v(8)/v(10)/v(11)/2v(9) and a set of spectroscopic constants for the v(8), v(10), and v(11) fundamentals as well as parameters for the "dark state" 2v(9), and fourteen coupling terms have been determined.