Non-Boltzmann, non-Treanor vibrational level populations of electrical discharge excited nitrogen

Abstract

Vibrational level population distributions of electrical discharge excited nitrogen were measured to v=5 using the electron beam fluorescence diagnostic technique. Measurements were made in the free jet expansion from an electrical discharge for both pure nitrogen and nitrogen–carbon monoxide mixtures. All measured distributions were highly non‐Boltzmann and also deviated from the Treanor quasisteady state distribution. A numerical matching technique was used to predict the shape of the vibrational population distribution for a given total vibrational population. The numerical results predict the shape of the distribution very well for all experimental conditions. The numerical modeling also showed that the deviation from Treanor conditions occurs because the V–V rates and electron excitation rates in the discharge are of the same order of magnitude for discharge pressures of a few Torr.