Kinetics of OH Radicals from Flame Emission Spectra. III. Total Transition Probabilities and the Energetic Distribution of OH(2Σ+) and O2(3Σu−) in the Oxy-Hydrogen Flame

The energetic distribution of OH(2Σ+) and O2(3Σu−) in hydrogen-oxygen flames has been investigated. The measurements were made in the inner cones of these flames burning with various fuel ratios (lean, stoichiometric, and rich) at atmospheric pressure. The relative concentrations of the excited species were determined by comparing the calculated equilibrium intensity ratios of OH(2Σ+) and O2(3Σu−) with the experimental intensity ratios. The electronic, vibrational, and rotational transition moments relevant to this calculation have been computed. The good agreement between the experimental intensity ratios and the calculated equilibrium intensity ratios indicates that the electronically excited O2(3Σu−) is in thermal equilibrium with OH(2Σ+). It is possible, therefore, that O2 is excited thermally in the hydrogen-oxygen flame.