Three-Body Recombination and Dissociation of Nitrogen: A Comparison between Theory and Experiment

Abstract

The modified phase-space theory of reaction rates is used to calculate the over-all recombination and dissociation rate coefficients of nitrogen in a heat bath of argon atoms. Substantial quantitative agreement is obtained between the theoretical predictions and the low-temperature (90–611°K) “discharge-flow-tube” measurements of the recombination rate coefficient and the high-temperature (8000–15 000°K) “shock-tube” measurements of the dissociation rate coefficient. The success of the theory in correlating the experimental measurements over such a wide temperature range clearly illustrates the importance of the weak attractive forces between the nitrogen and argon atoms for recombination at low temperatures, the marked reduction in the rates at high temperatures due to nonequilibrium distributions in the vibrational state populations of the molecules, and the major contribution to the over-all reaction rate coefficients due to reaction progress via the first electronically excited molecular state of nitrogen over the entire temperature range. The working relationships required for applying the modified phase-space theory to predict the dissociation and recombination rate coefficients of other diatomic molecules in the presence of weakly attracting collision partners, such as argon atoms, are summarized.