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

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1997

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Ohio State University

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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 radicalsb shows rotationally resolved absorption features that were assigned to the spin components of the bent-linear, B~2ΠX~2A 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 (CH2CO) using the loosely focused output from an ArF excimer laser (193nm). We have recorded vibronic and partially rotationally resolved LIF spectra of the B~2ΠX~2A 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.

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aThis work supported by the U. S. Department of Energy, office of Basic Energy Sciences, Chemical Sciences Division bD. 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

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