Overtone Spectroscopy of CHD3 in Liquid Argon Solutions

The vibrational overtone spectrum of CHD 3 has been obtained in liquid argon solutions at temperatures around 94 K. The spectra of C-H and C-D overtones below 10 000 cm −1 were obtained with a Fourier transform spectrophotometer operating in the near-infrared region and a low temperature cell. The C-H spectrum around Δv = 5 was recorded using a resonant photoacoustic technique at cryogenic temperatures. The absorption bands were computer deconvoluted to obtain the peak absorption frequency, the band-width, and the area of some important bands. Due to the small frequency shift of the absorption bands in solution with respect to the gas phase frequencies, the assignment of the transitions was made by comparison with experimental and calculated gas phase frequencies. The calculation of gas phase frequencies and vibrational states was made using the pure local mode model for the isolated C-H bond and the Harmonically Coupled Anharmonic Oscillator (HCAO) model for the three equivalent C-D bonds. In order to test the Fermi resonance interaction between C-H stretching and bending vibrations, the absorption bands and relative intensities in solution were used to obtain the parameters of an effective Fermi resonance Hamiltonian. The values of the parameters obtained in solution and gas phase are very close in magnitude. The optimized parameters of the Fermi resonance Hamiltonian give a good description of the frequencies and relative intensities of the C-H absorption bands in solution