REACTION OF H-ATOMS WITH N2O AT 374-628 K

The reaction of H atoms with N2O has been studied by flash photolysis in the temperature range 374-628 K at a pressure of 300 Torr, with arg on as the bath gas. H atoms were generated by photolysis of NH, and we re monitored by Lyman-a absorption. At these temperatures the reaction is slow, and care was taken to establish conditions that ensured the measured rate constants were not affected by the occurrence of heterog eneous or secondary reactions. The values obtained are a factor of two less than those reported previously (Marshall et al., J. Chem. Phys., 1987, 86, 5540; J. Phys. Chem., 1989, 93, 1922) over this range of te mperatures, and are given by /cm(3)s(-1)=(9.2+/-1.6)x10(-14)exp[(-2990 +/-90)/T] Combination of our rate constants with earlier high temperat ure data (Albers et al., 15th International Symposium on Combustion, T he Combustion Institute, Pittsburgh, PA, 1975, p. 765) confirms the cu rvature in the Arrhenius plot below 700 K observed previously. The com bined data, for the temperature range 374-1110 K, can be represented b y 1)=3.7x10(-10)exp(-8710/T)+2.2x10(-14)exp(-2340/T) Simulation of the reaction shows that our results are consistent with the notion that t he addition product HNNO is collisionally stabilized.