High-resolution FTIR spectroscopy of HCFC-31 in the 950 121160 cm 121region: rovibrational analysis and resonances in the \u3bd4, \u3bd9and \u3bd5+\u3bd6bands of CH235ClF

The FTIR spectrum of CH2ClF (natural isotopic mixture) was investigated in the \u3bd4, \u3bd9 and \u3bd5 + \u3bd6 band region between 950 and 1160 cm-1 at the resolution of 0.004 cm-1. The \u3bd4 and \u3bd5 + \u3bd6 vibrations of A\u2032 symmetry give rise to a/b hybrid bands with a predominant a-type component. The \u3bd9 vibration of A\u2033 symmetry, expected with a c-type band contour, shows an intense Coriolis-induced parallel component (\u394Ka = 0, \u394Kc = 0) derived from mixing with the \u3bd4 = 1 vibrational state. The high-resolution spectra of \u3bd9 and \u3bd5 + \u3bd6 have been analyzed for the first time, while the assignments of the \u3bd4 band, previously investigated, have been extended to higher J and Ka values in the b-type component. The spectral analysis resulted in the identification of 1508, 809 and 349 transitions for the \u3bd4, \u3bd9 and \u3bd5 + \u3bd6 bands of CH2 35ClF, respectively. Besides the strong first-order a- and b-type Coriolis resonances between \u3bd4 and \u3bd9, the \u3bd5 + \u3bd6 vibration was found to interact through a c-type Coriolis with the \u3bd4 and 3\u3bd6. High-order anharmonic resonance (\u394Ka = \ub12) between \u3bd4 and \u3bd5 + \u3bd6 was also established. All the assigned data were simultaneously fitted using the Watson's A-reduction Hamiltonian in the Ir representation and the relevant perturbation operators. The model employed includes five types of resonances within the tetrad \u3bd4/\u3bd9/\u3bd5 + \u3bd6/3\u3bd6. A set of spectroscopic constants for \u3bd4, \u3bd9 and \u3bd5 + \u3bd6 bands as well as parameters for the dark state 3\u3bd6 and seven coupling terms have been determined. The simulations performed in different spectral regions satisfactorily reproduce the experimental data