DIODE-LASER SPECTRUM AND ROVIBRATIONAL ANALYSIS OF THE NU-6 BAND OF VINYL FLUORIDE

The vibration-rotation spectrum of CH2=CHF has been investigated in the nu6 band region around 1305 cm-1 at Doppler limited resolution using a tunable diode laser spectrometer. The measurements have been performed at low temperature (240 K) to decrease hot band interferences. This fundamental of symmetry species A' gives rise to an a/b hybrid band, which was mainly composed of a-type transitions. Both J and K structures have been resolved in the (Q)Q(K)(J) subbranches and the rovibrational analysis in the P, Q, and R branches has led to the identification of more than 1000 lines with J less-than-or-equal-to 43 and K(a)' less-than-or-equal-to 14. The nu6 band is affected by first-order b-type and second-order a-type Coriolis resonances with the nu9 + nu11 combination, and the perturbation effect has been found stronger for the K(a)' = 11 level. About 870 transitions free of major resonance contributions were fitted using Watson's A-reduction Hamiltonian in the I(r) representation, and a set of effective rotational and quartic centrifugal distortion constants was determined for the upsilon6 =1 state of CH2=CHF.