Spectrokinetic studies of the gas phase reactions NH₂ + NO_x initiated by pulse radiolysis

NH2 radicals were produced by pulse radiolysis of Ar-SF6-NH3 mixtures to initiate the reaction F + NH3 → HF + NH2. Decay rates of NH2 were studied by monitoring the transient absorption signals of NH2 at 597.6 nm in the presence of varying amounts of NO and NO2. Values of κ(NH2 + NO) = (1.3 ± 0.2)×1010 M-1 s-1 and A:(NH2 + NO2) = (1.1 ± 0.3)×1010 M-1 s-1 were obtained at 298 K. By montitoring the transient absorption of OH radicals at 309 nm we have determined a very low branching for the reaction channel NH2 + NO → N2H + OH, suggesting that NH2 + NO → N2 + H2O is the most important product channel at room temperature. The analysis of the experimental results was based on computer modelling of the observed radical yields and kinetics, taking into account various competing reactions which were shown to be important by the evaluation of branching ratios.