			15min:

VIBRATIONAL OVERTONE SPECTRA OF C₂H₆ AND C₂H₄ IN CRYOGENIC LIQUIDS .

MARIA H. DIEZ-Y-RIEGA AND CARLOS E. MANZANARES, Department of Chemistry and Biochemistry, Baylor University, Waco, Texas, 76798.

Vibrational overtone spectra of C₂H₆ and C₂H₄ in cryogenic solutions were recorded between 5000 and 14000 cm^-1. Spectral regions for the first four overtones were measured using a Fourier transform spectrophotometer. The fifth overtone ( Delta =6) spectra between 15,000 and 16,000 cm^-1 were recorded with a double beam (pump-probe) thermal lens technique using concentrations as low as 10^-3 mole fraction. The peak frequency shift ( Delta omega ) from gas phase to solution is explained by the change in harmonic frequency and anharmonicity in solution with respect to the gas phase values. The bandwidth ( Delta omega _1/2) of the ( Delta = 6) C-H absorption bands in solution can be explained in terms of collisions with the solvent molecules.