High-Resolution Infrared Laser Study of the ν4 Absorption Band of cis-CHClCHF

Abstract cis -1-Chloro-2-fluoroethylene was synthesized, and the gas-phase infrared spectrum was investigated in the ν 4 band region between 1321–1350 cm −1 , at a resolution of about 0.002 cm −1 , employing a tunable diode–laser spectrometer. This vibration of symmetry species A ′ gives rise to an a / b -hybrid band, even though our analysis pointed out that the intensity of the a -type component is predominant. Most of the J and K structure was resolved in different subbranches, and the rovibrational analysis led to the assignment of about 1900 a -type lines with J ≤ 71 and K a ≤ 20 for the 35 Cl isotopic species. The ν 4 fundamental is locally perturbed by a weak Coriolis resonance and some local crossings were found; the 3ν 12 state seems to be the most likely interacting level. Using Watson's A -reduction Hamiltonian in the I r representation, a set of spectroscopic parameters for the v 4 = 1 state was obtained.