Absorption spectrum of trideuteromethane between 8 and 11.5 μm: Analysis of the ν3 and ν6 bands

The analysis of the absorption spectrum of 12CD3H, previously reported for the region 1200–1400 cm−1 concerned with the ν5 band, is now extended to cover the region 872–1213 cm−1 including the two bands ν3 and ν6. These are centered at 1004.553 and 1035.917 cm−1, respectively, and strongly coupled by a Coriolis interaction. A formulation taking this interaction into account rigorously was used; as a result, the energies for the upper states v3 = 1 and v6 = 1 are derived as eigenvalues of an effective Hamiltonian (J. Mol. Spectrosc. 79, 31–46 (1980)). The fit of the upper-state constants based on 1434 observed transitions including J′ and K′ values up to 22 leads to a set of 22 significant values which reproduce the observed wavenumbers with a standard deviation of 0.007 cm−1 close to the experimental uncertainties.