			15min:

HIGH RESOLUTION, NEAR AND MID IR, JET-COOLED, CAVITY RING-DOWN SPECTROSCOPY WITH A NOVEL DISCHARGE EXPANSION.

SHENGHAI WU, PATRICK DUPRÉ AND TERRY A MILLER, Department of Chemistry, The Ohio State University, 120 W. 18^th Ave., Columbus OH, 43210.

The frequency coverage of our CRDS spectrometer has been extended from the 1.0 -- 1.5 µm region to the 3 -- 3.5 µm region, which opens exciting opportunities for studying the C-H fundamental vibrational modes of molecules and free radicals. Furthermore, higher resolution has been provided by using difference frequency generation (DFG) based on a Fourier transform limited Ti:Sapphire pulse-amplified laser. As an example, the jet-cooled spectra of the CH₃ radical with partially resolved hyperfine structures will be presented. Non-exponential effects in the ring-down decay have also been minimized by using the narrow bandwidth radiation.

Additionally, a novel transverse discharge arrangement had been designed to improve stability, and also to provide a capability of mixing chemical reagents downstream. We will present preliminary spectral results and kinetic analyses characterizing this radical source.