Vibrational overtone spectroscopy of CH2D2 in liquid argon solutions

The spectra of the fundamental and overtones of the C-H (nu = 1-5) and C-D (Delta nu = 1, 2, 3) stretches of CH2D2 have been measured in liquid argon solutions at temperatures between 94 and 101 K. Absorption in the visible was obtained with a low temperature cell and a resonant continuous wave laser technique with acoustic detection. Absorptions in the IR and near-IR were observed with a Fourier transform spectrophotometer. To interpret the experimental results, overtone transitions are described in terms of the local mode model. The harmonically coupled anharmonic oscillator (HCAO) model was used to determine the overtone energy levels and assign the absorption bands to vibrational transitions. The linewidths of the fundamental and overtone transitions are discussed in terms of rotational relaxation for the fundamental bands and vibrational relaxation in the form of dephasing for the overtones.