# LASER-INDUCED FLUORESCENCE SPECTROSCOPY OF THE HCCO $RADICAL^{a}$

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 Title: LASER-INDUCED FLUORESCENCE SPECTROSCOPY OF THE HCCO $RADICAL^{a}$ Creators: Brock, L. R.; Mischler, Bernard H.; Rohlfing, Eric A.; Bise, Ryan T.; Neumark, Daniel M. Issue Date: 1997 Publisher: Ohio State University Abstract: The ketenyl radical, HCCO, is a critical intermediate in the oxidation of acetylene in combustion. Despite its importance, spectroscopic characterization of electronic transitions in this radical have remained elusive. A recent photofragment yield (PFY) spectrum of a mass-selected beam of HCCO $radicals^{b}$ shows rotationally resolved absorption features that were assigned to the spin components of the bent-linear, $\tilde{B}^{2}\Pi - \tilde{X}^{2}A^{\prime\prime}$ transition. Based on the PFY spectra we have obtained laser-induced fluorescence (LIF) spectra of jet-cooled HCCO for the first time. The jet-cooled ketenyl radicals are produced in the initial portion of a helium free-jet expansion by photolysis of ketene $(CH_{2}CO)$ using the loosely focused output from an ArF excimer laser (193nm). We have recorded vibronic and partially rotationally resolved LIF spectra of the $\tilde{B}^{2}\Pi-\tilde{X}^{2}A^{\prime\prime}$ system in the 300 nm region. Comparisons between the LIF and PFY spectra will be presented and the predissociation of the excited state will be discussed. Description: $^{a}$This work supported by the U. S. Department of Energy, office of Basic Energy Sciences, Chemical Sciences Division $^{b}$D. L. Osborn, H. Choi, D. H. Mordaunt, R. T. Bise, D. M. Neumark and C. M. Rohlfing, J. Chem. Phys. (1997), in Press. Author Institution: Combustion Research Facility, Sandia National Laboratories; Department of Chemistry, University of California URI: http://hdl.handle.net/1811/14057 Other Identifiers: 1997-TD-07