High-resolution infrared laser study of the nu(4) absorption band of cis-CHCl=CHF

cis-1-Chloro-2-fluoroethylene was synthesized, and the gas-phase infrared s pectrum was investigated in the v(4) band region between 1321-1350 cm(-1), at a resolution of about 0.002 cm(-1), employing a tunable diode-laser spec trometer. 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-typ e component is predominant. Most of the J and K structure was resolved in d ifferent subbranches, and the rovibrational analysis led to the assignment of about 1900 a-type lines with J less than or equal to 71 and K-a less tha n or equal to 20 for the Cl-35 isotopic species. The v(4) fundamental is lo cally perturbed by a weak Coriolis resonance and some local crossings were found the 3v(12) state seems to be the most likely interacting level. Using Watson's A-reduction Hamiltonian in the I-r representation, a set of spect roscopic parameters for the v(4) = 1 state was obtained. (C) 1999 Academic Press.