Infrared laser spectroscopy and rovibrational analysis of the ν5 fundamental of cis-1-chloro-2-fluoroethylene

The infrared spectrum of cis-1-chloro-2-fluoroethylene (cis-CHClCHF) has been investigated in the ν5 band region between 1220 and 1250 cm−1, at a resolution of about 0.002 cm−1, using a tunable diode laser spectrometer. This fundamental of symmetry species A′ yields a strong a/b-hybrid band with contributions of comparable intensity from both the components. The rovibrational analysis led to the identification of 3800 lines (J⩽69, Ka⩽25) for the ν5 band of 35Cl species, whose origin is at 1231.849 cm−1. Using Watson's A-reduction Hamiltonian in the Ir representation, a set of spectroscopic parameters up to sextic centrifugal distortion terms was obtained for the v5=1 state, which turned out to be free from perturbations.