High resolution infrared synchrotron study of CH₂D⁸¹Br: ground state constants and analysis of the ν₅, ν₆ and ν₉ fundamentals

The high resolution infrared absorption spectrum of CH2D81Br has been recorded by Fourier transform spectroscopy in the range 550–1075 cm1, with an unapodized resolution of 0.0025 cm-1, employing a synchrotron radiation source. This spectral region is characterized by the ν6 (593.872 cm-1), ν5 (768.710 cm-1) and ν9 (930.295 cm-1) fundamental bands.

The ground state constants up to sextic centrifugal distortion terms have been obtained for the first time by ground-state combination differences from the three bands and subsequently employed for the evaluation of the excited state parameters. Watson’s A-reduced Hamiltonian in the Ir representation has been used in the calculations.

The ν6=1 level is essentially free from perturbation whereas the ν5=1 and ν9=1 states are mutually interacting through α-type Coriolis coupling. Accurate spectroscopic parameters of the three excited vibrational states and a high-order coupling constant which takes into account the interaction between ν5 and ν9 have been determined.