Diode laser spectrum and rovibrational study of the ν6 fundamental of vinyl bromide

Abstract The gas-phase infrared spectrum of natural CH 2 CHBr has been investigated in the ν 6 band region near 1258 cm −1 , at a resolution of about 0.002 cm −1 , using a tunable diode laser spectrometer. This vibration of symmetry species A ′ yields an a / b hybrid band exhibiting predominant characteristics of the a -type component. Spectral analysis resulted in the assignment of 359 ( J ≤31, K a ≤7) and 351 ( J ≤50, K a ≤6) transitions of the ν 6 fundamental of 79 Br and 81 Br isotopomers, respectively, whose band origin is separated by 0.0207 cm −1 . The assigned transitions, fitted using Watson's A-reduction Hamiltonian in the I r representation, yielded upper state constants up to the quartic coefficients for both the isotopic species. The ν 6 vibration is locally perturbed by a second order a -type Coriolis resonance with the ν 9 + ν 11 state and the coupling constant as well as the band origin for the perturber were determined.