High-resolution infrared spectrum of CHD₂⁷⁹Br: ro-vibrational analysis of the ν₅ and ν₉ fundamentals

The high-resolution infrared spectrum of CHD279Br has been investigated by Fourier transform spectroscopy in the range 700–900 cm−1 at an unapodized resolution of 0.0035 cm−1. This spectral region is characterised by the absorptions of the ν5 (814.5185 cm−1) and ν9 (716.9649 cm−1) fundamental bands, corresponding to H–C–Br deformation and CD2 rocking modes, respectively.

The ν5 vibration of symmetry species A′ gives rise to an a-/c-hybrid band with a predominant a-type component, while the ν9 mode of A′′ symmetry produces a b-type envelope. The spectral analysis resulted in the identification of 5290 (J′ ≤ 63 and Ka′ ≤ 13) and 1657 (J′ ≤ 53 and Ka′ ≤ 12) transitions for ν5 and ν9 bands, respectively.

The assigned data were fitted using the Watson’s S-reduced Hamiltonian in the Ir representation and the v5 = 1 and v9 = 1 state parameters up to the quartic centrifugal distortion terms have been obtained. From spectral simulations the dipole moment ratio |Δμa/Δμc| of the ν5 band has been determined to be 1.4 ± 0.1 while the intensity ratio between ν5 and ν9 fundamentals has been estimated to have a value of 4.3 ± 0.5.