High resolution FTIR spectroscopy of chlorofluoromethane near 13 µm: rovibrational analysis and resonances of ν5and 2ν6bands in ClF and ClF

The FTIR spectra of CH2ClF (natural isotopic mixture) and ClF (isotopically enriched sample) were investigated in the ν5 and 2ν6 region between 700 and 800 cm-1 at a resolution of 0.004 cm-1. The ν5 and 2ν6 vibrations of A′ symmetry give rise to a/b hybrid bands with a very predominant a-type component. Due to the proximity of their band origins, the v 5 = 1 and v 6 = 2 levels perturb each other by Fermi and Coriolis resonances. The interaction mechanisms, previously investigated in the rotational spectra of ClF, were extended to the less abundant isotopic species ClF and to higher J and Ka values in the main isotopologue. The spectral analysis resulted in the identification of 4188 and 5392 transitions for ClF and ClF, respectively. All the assigned data were simultaneously fitted using the Watson's A-reduction Hamiltonian in the I r representation and perturbation operators. Excited state parameters, band origins and coupling terms for the ν5/2ν6 dyad of both isotopologues were determined.