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.

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The yield of oxygen and hydrogen atoms through dissociative recombination of H2O+ ions with electronsThree-body recombination and dissociation rate coefficients (k, and k,p respectively) for the reactions H2 + H~H + H + H have been evaluated for temperatures ranging between 300 and 10 OOOoK on the basis of the modified phase-space theory of reaction rates and Monte Carlo trajectory calculations. The semiempirical Porter-Karplus surface for H3 was used in the· calculations. Good agreement was obtained between the theoretical estimates of kd and the bulk of the dissociation rate measurements. However, in contradistinction to some of the recent experimental investigations, neither the extremely steep temperature decay (<» T -6) of k, at high temperatures nor the existence of a pronounced maximum in k, at moderate temperatures are supported by this theoretical work. Possible reasons for these differences are suggested. A simple ratio was deduced which relates I4 H ) and the corresponding rate coefficients of the isotopes of hydrogen. The result is in good agreement with available experimental measurements and enables one to predict the latter rate coefficients without additional trajectory calculations. An example is given to illustrate the capability of the present Monte Carlo method in obtaining other useful information about atomic and molecular collision processes.

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