VIBRATIONAL SPECTROSCOPY OF C-H BONDS OF C2H4 LIQUID AND C2H4 IN LIQUID ARGON SOLUTIONS

The spectra of the fundamental and first and second overtones (Delta nu = 1, 2, and 3) around the C-H stretch of ethylene in liquid argon solutions have been measured at 88 K. The IR, near-IR, and visible spectra of pure liquid ethylene have been measured in the range from 2800 to 15 000 cm(-1) at 109 K. Absorptions in the visible were obtained with a low-temperature cell and a resonant continuous wave laser technique with acoustic detection. Absorptions below 12 000 cm(-1) were observed at low temperatures with a Fourier transform spectrophotometer operating in the near-IR region. Comparison is made between the absorption bands of gas phase, liquid argon solution, and liquid phase ethylene. Spectra of solutions of ethylene in liquid argon show great simplification of the bands with respect to the room temperature gas-phase absorption bands. Due to the small frequency shift in solution, assignments are presented based on gas-phase measurements. For the C-H transitions of pure liquid ethylene, the local mode harmonic frequency and anharmonicity are obtained and used with a harmonically coupled anharmonic oscillator (HCAO) model to calculate the energy of the levels and assign the absorption bands to particular transitions.