MEASUREMENT OF OH ROTATIONAL TEMPERATURES IN A FLAME USING DEGENERATE 4-WAVE MIXING

Temperatures have been measured in a laminar premixed propane–air diffusion flame using degenerate four-wave mixing (DFWM) of the OH radical. The spectra were recorded simultaneously with laser-induced fluorescence through the (0, 0) band of the OH A2Σ-X2II transition. Individual rotational lines are more clearly resolved in the DFWM spectrum than in the laser-induced fluorescence spectrum, although both are power broadened at laser intensities of 1-2 MW/cm2 at 307 nm. Rotational temperatures have been determined from the DFWM spectra and are in close agreement with temperatures measured with coherent anti-Stokes Raman spectroscopy of nitrogen. © 1990 Optical Society of America.