Rotational Temperatures of OH in Several Flames

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Abstract
The intensity of OH emission from various small regions of Bunsen‐type flames of hydrogen, acetylene, methane, and propane, premixed with oxygen, has been observed spectroscopically and corresponding rotational temperatures have been determined by an iso‐intensity method. An ultraviolet grating monochromator of high resolution was used; fuel to oxygen ratios were varied from about 0.5 to 2 times the stoichiometric value; and rotational temperatures were determined at several positions within each flame. The measured temperatures of the reaction zone varied little with mixture ratio for a given fuel and were greater than adiabatic, suggesting a lack of thermal equilibrium. In the hot gases beyond the reaction zone, however, evidence was found of both rotational and electronic equilibrium. The concentration of thermally produced OH in the burned gases was found to be so great that it tends to mask the emission from the reaction zone.