KINETICS AND BRANCHING RATIOS OF THE REACTIONS NH2-]N2O+H2O AND NH2+NO2-]H2NO+NO STUDIED BY PULSE-RADIOLYSIS COMBINED WITH TIME-RESOLVED INFRARED DIODE-LASER SPECTROSCOPY(NO2)

The source reaction F + NH3 --> HF + NH2 was initiated by the pulse ra diolysis of NH3/SF6 mixtures, and the primary yield of F atoms was det ermined by monitoring the decrease in the infrared absorption of metha ne consumed in the titration reaction F + CH4 --> HF + CH3. The title reactions have been studied by monitoring the decay of NH2 and the sim ultaneous formation of N2O and NO by time-resolved infrared diode lase r 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) X 10(-11) molecule(-1) cm(3) s(-1) at 298 K and with a bath gas pressure of p(SF6) = 40 mbar. Two product channels have been iden tified, N2O + H2O and H2NO + NO, with relative yields of (59 +/- 3)% a nd (40 +/- 5)%, respectively.