Kinetics and branching ratios of the reactions NH 2 + NO 2 → N 2O + H 2O and NH 2 + NO 2 → H 2NO + NO studied by pulse radiolysis combined with time-resolved infrared diode laser spectroscopy

Abstract

The source reaction F + NH 3 → HF + NH 2 was initiated by the pulse radiolysis of NH 3/SF 6 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 + CH 4 → HF + CH 3. The title reactions have been studied by monitoring the decay of NH 2 and the simultaneous formation of N 2O and NO by time-resolved infrared diode laser spectroscopy. The decay rate of NH 2 was studied as a function of NO 2 concentration to obtain an overall rate constant k(NH 2 + NO 2) = (1.35 ± 0.15) × 10 −11 molecule −1 cm 3 s −1 at 298 K and with a bath gas pressure of p(SF 6) = 40 mbar. Two product channels have been identified, N 2O + H 2O and H 2NO + NO, with relative yields of (59 ± 3)% and (40 ± 5)%, respectively.