15min:
CAVITY RING DOWN AT LOW TEMPERATURES: VIBRATIONAL OVERTONE ABSORPTION OF DEUTERATED METHANES AT 110 K.

Y. PEREZ-DELGADO AND CARLOS E. MANZANARES, Department of Chemistry and Biochemistry, Baylor University, Waco, Texas, 76798.

The C-H stretch overtone absorptions of ( Delta upsilon = 5) of CH4, CH3D, CH2D2, and CHD3 have been obtained using the phase shift cavity ring down technique. A low temperature cell was designed and adapted to the CRD experiment to measure absorption bands at any temperature between 10 K and 298 K. The spectra were obtained at room temperature and at 110 K. The partially resolved rotational spectrum of CHD3 that included the transitions 5 nu1 and 4 nu1+2 nu5 was obtained and compared with the calculated spectrum. The unresolved vibrational bands around the Delta upsilon = 5 region of CH2D2, CH3D, and CH4 were also obtained at several temperatures between 100K and 298 K. The integrated absorption was calculated as a function of the density of the gas samples and used to obtain the cross section and the oscillator strength of the transition for each molecule.