A general model for the spectral calculation of OH radiation in the ultra violet

A new spectroscopic model is discussed that permits the calculation of OH spectra in the ultraviolet for the range of gas dynamics conditions observed in hypersonic flows. This requires a vibration-electronic excitation model sufficiently general to account for the diversity of collision rates that leads to conditions ranging from equilibrium to the collisionless-lifetime regimes. At sufficiently high gas temperatures predissociation, and the reverse process, from higher lying rotational states in the zero and first vibrational states of the excited state must also be considered. Although the structure of the Oil (A → X) spectra are complex, accurate line positions and transition probabilities are available and have been used. This paper will discuss the full excitation and spectral model and provide examples that demonstrate its generality. Detailed comparisons are presented with experimental spectra measured under radically different conditions. The first spectrum was measured at atmospheric pressure in a plasma generated by a 50 kW Radio-frequency plasma torch. The second spectrum was measured under rarefied conditions in the bow shock of a reentering rocket.