Rotational and Vibrational ``Temperatures'' of CH in Flames at Atmospheric Pressure

Spectra of the R branch of the 2Δ—2Π transition of CH have been obtained from flames of acetylene, propane, and methane premixed with oxygen burning at atmospheric pressure. The distributions of rotational and vibrational intensities have been measured and compared with those expected from thermal excitation. Although in some flames the distributions are close to thermal, the majority of distributions indicate that the excited CH is formed by a nonthermal process and is unreliable as a temperature indicator. The suppression of predissociation of CH in rich hydrogen flames with added acetylene has also been investigated. A continuous emission reaching a maximum near 4000A has been measured.