Rate constants for the N2O reaction system: Thermal decomposition of N2O; N+NO→N2+O; and implications for O+N2→NO+N

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Abstract
Experiments on the thermal decomposition of N2O have been carried out in reflected shock waves using the atomic resonance absorption spectrometric (ARAS) technique for monitoring the product O atoms. The results provide a calibration for the ARAS system as well as values for the decomposition rate constant, k1, between 1540 and 2500 K. The present results can be represented as k1=5.25×10−10 exp(−27 921 K/T) cm3 molecule−1 s−1. Additionally, rate constants for the reaction, (2) N+NO→N2+O, have been measured by the laser photolysis‐shock tube (LP‐ST) technique between 1251 and 3152 K. NO serves as both the photolytic source of N(4S) atoms and the reactant molecule. N atoms are monitored by the ARAS method. The results do not show significant temperature dependence and can be represented by k2=(3.7±0.8)×10−11 cm3 molecule−1 s−1 over the experimental temperature range. Values for the reaction, (−2) O+N2→NO+N, can be derived from these results. The results are compared with earlier studies and are then theoretically discussed in terms of transition states taken from an ab initio electronic structure calculation and also from a dispersion force model. Neither model accurately predicts the observed behavior, and this suggests that further theoretical work with trajectory calculations be attempted to assess the importance of recrossing.

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