HIGH-RESOLUTION INFRARED MEASUREMENTS AND ANALYSIS OF THE NU(4) BAND OF CF2=CHF

The nu(4) band of CF2=CHF near 1265 cm(-1) has been studied at a resol ution of ca. 0.002 cm(-1) using spectra obtained with a tunable diode laser spectrometer. This vibration, of A' symmetry, gives rise to a ty pe ab hybrid band where the a-type component dominates. The rovibratio nal analysis led to the assignment of about 3000 transitions with J le ss than or equal to 80, K-a less than or equal to 33, and K-c less tha n or equal to 80. The band is locally perturbed by first-order b-type Coriolis resonance with the close-lying levels (nu(8) + nu(9) + nu(11) /2 nu(8) + nu(12)), and some local crossings have been found. Even tho ugh no transitions to the perturbing levels have been observed, some p arameters for the perturber were determined from the interaction effec ts near the crossings. Using Watson's A-reduction Hamiltonian in the I -r representation, a set of effective constants for the upsilon(4) = 1 state has been derived employing transitions free of major resonance effects. (C) 1997 Academic Press.