Abstract

Two-photon-excited fluorescence (TPF) has been used to determine the OH concentration profile in an atmospheric-pressure hydrogen–oxygen flame. Individual rovibronic transitions within the A²Σ⁺−X²Π (0,0) system of OH were identified by comparing calculated wavelengths to emission spectra obtained by laser excitation from 604 to 638 nm. Relative OH concentrations were determined by individually exciting the O₁(5), O₂(5), and P₂(5) transitions and monitoring the resulting fluorescence with a filtered photomultiplier and a gated integrator system. The expected quadratic dependence of the fluorescence signal on laser power was verified indicating the probable lack of photochemical effects. The OH profile determined by the TPF method was found to be in good agreement with that determined by absorption spectroscopy. The estimated OH detection limit using TPF is ∼10¹⁴ molecules/cm³ at atmospheric pressure.

© 1986 Optical Society of America

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