High-resolution FTIR analysis of the 2v6 overtone of cis-CHF=CHF and Fermi resonance study with the v2 fundamental

The 2v6 overtone band (1659.43 cm-1) of cis-CHF=CHF has been recorded with an unapodized resolution of 0.004 cm-1, using a multipass cell and a Fourier transform infrared spectrometer. More than 2300 transitions have been assigned and fitted to the Watson's A-reduced Hamiltonian in the Ir representation yielding accurate spectroscopic parameters up to three sextic coefficients. The vibrational resonance of 2v6 with the v2 fundamental was also considered and, as a result, the Fermi coupling term, the unperturbed vibrational levels and molecular parameters have been calculated. Additionally, information on the infrared inactive v6 vibration have been derived.