Elementary combustion processes in cyanogen +oxygen + hydrogen flames: Spectroscopic studies

Visible and ultraviolet spectra of reduced pressure C 2 N 2 +O 2 +H 2 flames have for the first time been subjected to a detailed investigation. Rotational and vibrational temperatures of CN ( X 2 σ + ) are found to be in close agreement, as are those of CN ( B 2 σ + ). Upper-state temperatures of a given species always exceed the lower-state values. These conclusions are in line with previous, analogous observations on the ground and accessible upper states of OH, CH, and C 2 in C 2 H 2 +O 2 flames. The vibrational and rotational temperatures of C 2 (A 3 H g ) and CN ( B 2 σ + ) are broadly similar, lying in the general range 5500°–6500°K. The (rotational) temperature of CN ( X 2 σ + ) appears to be quite normal, and would thereby seem to provide a satisfactory measure of translational temperature for this system. Sodium D-line reversal temperatures are also normal away from the reaction zone, but (in contrast to the situation with C 2 H 2 +O 2 flames) are well above thermal in the reaction zone itself. Measured concentrations of CN ( X 2 σ + ) (in O 2 -rich flames, at least) are many orders-of-magnitudeabove thermal. In contrast, neither C 2 ( X 3 II u ) nor CH ( X 2 II) could be detected at all, even in the most fuel-rich flames, and there are good grounds for believing that the concentrations of these species are, in fact, below the equilibrium values.