High-resolution infrared and ab initio investigation of CHD2⁷⁹Br: Ro-vibrational analysis of the ν6 fundamental and the 2_ν6−ν6 hot band

The high-resolution infrared spectrum of CHD279Br has been investigated by Fourier transform spectroscopy in the range 540–615 cm−1 at an unapodised resolution of 0.0035 cm−1. This spectral region is characterised by the ν6 fundamental (584.8510 cm−1), corresponding to C–Br stretching mode, and its hot band 2ν6−ν6 (578.4333 cm−1). The spectral analysis resulted in the identification of 3430 transitions (J’ ≤ 73 and K'a ≤ 18) for the ν6 fundamental and 1212 transitions (J’ ≤ 49 and K'a ≤ 11) for the hot band 2ν6−ν6. The assigned data have been fitted using the Watson’s S-reduced Hamiltonian in the Ir representation and new constants for the ground state from about 24,600 combination differences and sets of parameters for the v6 = 1 and 2 vibrational states have been obtained. From spectral simulations the intensity ratio between 2ν6−ν6 and ν6 has been estimated to be 0.15 ± 0.02. High-quality ab initio calculations have also been performed at the CCSD(T) level of theory in order to support the experimental investigation through the calculation of molecular parameters relevant to ro-vibrational spectroscopy.