CW Ion Laser Excitation of OH and NH in an Atmospheric Pressure Flame

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1983

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Ohio State University

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Intense laser fluorescences of the important NH and OH radicals In a flame have been observed upon excitation by the 3507 \AA line of a krypton ion laser. The experimental apparatus was very similar to that described in detail $previously^{1}$ for use in laser Raman and fluorescence flame investigation. Briefly, a lean $CH_{4}/N_{2}O/N_{2}$ flame ($-$2500K flame temperature) was placed inside the extended cavity of a 3 w (all lines) krypton laser with prism tuned line selection. Fluorescence excited by the laser was detected by a 25 cm monochromator equipped with a silicon intensified vidicon tube. When the laser was tuned to 3507\AA, intense fluorescences of NH and OH above the flame emission were observed. A simple differencing technique allowed for removal of the flame emission from the fluorescence spectra. The fluorescence spectra, combined with detailed calculation of line positions, lead to the following tentative assignments of pumping transitions: NH, A-X (0,0) $^{O}P_{23} 21$; OH, A-X (0,1) $O_{1} 19$. However, some ambiquity still exists concerning these assignment. The observed spectra and assignment will be discussed. $^{1}$ W.R. Anderson, J.A. Vanderhoff, A.J. Kotlar, M.A. DeWilde, and R.A. Beyer, J. Chem. Phys., 77, 1677 (1982).

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Author Institution: Ballistic Research Laboratory.

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