High-resolution FTIR spectroscopy of HCFC-31 in the 950−1160 cm region: rovibrational analysis and resonances in the ν 4 , ν 9 and ν 5 +ν 6 bands of CH 2 ClF.

The FTIR spectrum of CH2ClF (natural isotopic mixture) was investigated in the ν4, ν9 and ν5+ν6  band region between 950 and 1160 cm−1at the resolution of 0.004 cm−1. The ν4and  ν5+ν6  vibrations of A′ symmetry give rise toa/bhybrid bands with a predominanta-type component. The ν9vibration of A″symmetry, expected with ac-type band contour, shows an intense Coriolis-induced parallel component (ΔKa= 0, ΔKc= 0) derived from mixing with thev4= 1 vibrational state. The high-resolution spectra of ν9and   ν5+ν6  have been analyzed for the first time, while the assignments of the ν4band, previously investigated, have been extended to higherJandKavalues in theb-type component. The spectral analysis resulted in the identification of 1508, 809 and 349 transitions for the ν4, ν9and ν5+ν6  bands of CH235ClF, respectively. Besides the strong first-ordera-andb-type Coriolis resonances between ν4and ν9, the  ν5+ν6  vibration was found to interact through ac-type Coriolis with the ν4and 3ν6. High-order anharmonic resonance (ΔKa= ±2) between ν4and  ν5+ν6  was also established. All the assigned data were simultaneously fitted using the Watson's A-reduction Hamiltonian in theIrrepresentation and the relevant perturbation operators. The model employed includes five types of resonances within the tetrad ν4/ν9/ν5+ν6/3ν6. Α  set of spectroscopic constants for ν4, ν9and ν5+ν6bands as well as parameters for the dark state 3ν6and seven coupling terms have been determined. The simulations performed in different spectral regions satisfactorily reproduce the experimental data. [ABSTRACT FROM PUBLISHER]