The high-resolution fourier transform spectrum of dideuterated methane CH₂D₂ in the region between 1900 and 2400 cm^-1

The infrared spectrum of doubly deuterated methane CH₂D₂ has been recorded in the region from 1900 to 2400 cm^-1 at almost Doppler-limited resolution by using two high-resolution Fourier transform spectrometers. The vibrational bands observed include 2ν₄, ν₄ + ν₇, 2ν₇, ν₂, ν₈, ν₄ + ν₉, and ν₇ + ν₉, which were analyzed by taking into account Coriolis and Fermi interactions among them and also those with ν₄ + ν₅, ν₃ + ν₇, and ν₅ + ν₇. Most of the centrifugal distortion constants were constrained to appropriate values, while the vibrational term value and three rotational constants in each of the seven excited states were adjusted along with Coriolis and Fermi interaction parameters by the least-squares analysis of the observed spectrum. The vibration-rotation interaction constants α_s thus determined for the ν₂ and ν₈ states were combined with those of other fundamental states already published to calculate the equilibrium C-H distance.