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

Abstract

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 ¹Δ⁻_g ← X ³Σ⁻_g of O₂ and B ³Π_g ← A ³Σ⁺_u of metastable N₂ and vibrational overtones of H₂O (polyad 2) and the OH radical. Fundamental vibrational transitions of CH₃ (ν₃) 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.