NEAR-INFRARED AND VISIBLE SPECTROSCOPY OF CH3D IN LIQUID ARGON SOLUTIONS

The near-infrared and visible spectra of CH3D in liquid argon solutions have been measured around 95 K. The fundamental and overtones, Δv = 1, 2, 3, 4, and 5 around the C−H stretch and Δv = 1, 2, and 3 of the C−D stretch, are reported. Combination bands between 3500 and 5000 cm-1 (Δv = 3/2) and between 6500 and 7600 cm-1 (Δv = 5/2) of the C−H stretching vibration were also measured. Measurements were made using a cryostat, a low-temperature cell, and a Fourier transform IR and near-IR spectrometer. Visible spectra were recorded with a photoacoustic spectrometer employing resonant continuous wave laser excitation and piezoelectric detection. Spectra in solutions are greatly simplified compared to the gas phase. This simplification is attributed to a narrowing of the rotational distribution at low temperatures and partial hindering of the rotational motion of sample molecules. Peak positions are systematically red-shifted with respect to the gas phase, and the magnitude of the shift increases with the vibra...