High-resolution infrared spectroscopy of CH281BrF near 8 μm: rovibrational analysis of the v3 and v8 fundamentals and resonances with the dark states 2v5 and v6 + v9

The infrared spectrum of isotopically enriched (CH2BrF)-Br-81 was investigated in the.3 and.8 region between 1150 and 1370 cm(-1) at a resolution of 0.003 cm(-1). The v(3) vibration of symmetry species A' gives rise to an a-/b-hybrid band with a-type predominance, while the.8 mode of A '' symmetry produces c-type absorption. Due to the proximity of the band origins to those of closely lying overtones and combination bands, the v(3) = 1 and v(8) = 1 levels were found perturbed through Coriolis resonance by the v(5) = 2 (A') and v(6) = v(9) = 1 (A '') states, respectively. The spectral analysis resulted in the identification of 3132 transitions (J '' <= 98 and K-a '' <= 14) for the v(3) and 2958 transitions (J '' <= 68 and K-a '' <= 19) for the v(8) bands. The assigned data were fitted using theWatson's A-reduction Hamiltonian in the I-r representation and the perturbation operators. Although no transitions belonging to the perturbers were observed, the band origins and excited state parameters for fundamentals and ` dark states' together with coupling terms for the v(3)/2v(5) and v(8)/v(6) + v(9) dyads were determined.