Kinetics and branching ratios of the reactions NH2 + NO2 → N2O + H2O and NH2 + NO2 → H2NO + NO studied by pulse radiolysis combined with time-resolved infrared diode laser spectroscopy

The source reaction F + NH3 → HF + NH2 was initiated by the pulse radiolysis of NH3/SF6 mixtures, and the primary yield of F atoms was determined by monitoring the decrease in the infrared absorption of methane consumed in the titration reaction F + CH4 → HF + CH3. The title reactions have been studied by monitoring the decay of NH2 and the simultaneous formation of N2O and NO by time-resolved infrared diode laser spectroscopy. The decay rate of NH2 was studied as a function of NO2 concentration to obtain an overall rate constant k(NH2 + NO2) = (1.35 ± 0.15) × 10−11 molecule−1 cm3 s−1 at 298 K and with a bath gas pressure of p(SF6) = 40 mbar. Two product channels have been identified, N2O + H2O and H2NO + NO, with relative yields of (59 ± 3)% and (40 ± 5)%, respectively.