Chemically Induced Vibrational Excitation: Hydroxyl Radical Emission in the 1–3 Micron Region Produced by the H+O3 Atomic Flame

Abstract

A detailed investigation has been performed in the 1‐ to 3‐μ wavelength region on the radiation emitted by the hydroxyl radical from a low‐pressure flame of ozonized oxygen and atomized hydrogen. Wavelengths and photon intensities have been obtained for about 300 lines in the OH vibration‐rotation bands V—V—ΔV where ΔV=3, V=9 to 5, and for ΔV=2, V=9 to 2. Relative photon band intensities have been determined from the overdetermined set of data by a method of successive approximations using an IBM 650 computer. Dipole moment parameters have been calculated using the above data and Morse oscillator transition probabilities. Approximate rotational and vibrational Boltzmann distributions exist with an average rotational ``temperature'' of 560°K for the P branches, 460°K for the R and Q branches, and a vibrational ``temperature'' of 9250°K for the ΔV=2 and 3 bands. The absence of radiation from levels V>9 confirms the nonthermal character of the excitation and its dependence on the energetics of the reaction O₃+H→OH+O₂. Moreover, flux calculations based on the assumption that in this case collisional deactivation transition probabilities are proportional to the radiation probabilities show that there is an appreciable OH production in all levels V≤9 and the main flux of OH through any population level is via ΔV=1 transitions. Possible causes for the large changes in line intensity with pressure and smaller but significant changes with flows or concentrations are discussed.