High-resolution IR cavity ring-down spectroscopy of jet-cooled free radicals and other species

Initial spectral results are reported from a newly constructed cavity ringdown spectrometer. The apparatus incorporates a slit-jet expansion, with or without a discharge, to produce cold sample molecules. High spectral resolution in both the near- and mid-IR is obtained by using stimulated Raman scattering of the pulsed amplified output of a cw Ti:Sa ring laser. Molecular spectra presented include the electronic near-IR transitions a (1)Delta(-)(g) <- X-3 Sigma(-)(g) of O(2)and (BIIg)-I-3 <- A(3)Sigma(+)(u) of metastable N-2 and vibrational overtones of H2O (polyad 2) and the OH radical. Fundamental vibrational transitions of CH3 (nu(3)) in the mid-IR are also observed. This apparatus has demonstrated the potential for obtaining high-resolution spectra of both reactive and non-reactive species throughout the entire IR region.