Excitation of spectra of OH in hydrogen flames and its relation to excess concentrations of free atoms

Abstract

Measurements have been made of the rotational and vibrational intensity distribution of OH bands in oxygen + hydrogen + nitrogen flames. Simultaneous observations have been made of the strength of Na and Li lines and their variation with height in the flame. The anomalously strong excitation of OH bands with v ' = 2 and 3 is accompanied by selective excitation of the f 1 spin levels of the 2 ∑ + state. This confirms that the anomaly results from an inverse predissociation, associated with an excess of free atoms in the flame gases. This excess is most important for the cooler flames and near the base of these flames. There is also strong excitation of the (0, 0) band of OH near the reaction zone and the mechanism for this is briefly discussed.