REACTIONS OF N(4S) ATOMS WITH NO AND H-2

Reactions of N(4S) atoms with NO and H2 have been investigated using direct detection of N atoms by the atomic resonance absorption technique in a shock tube apparatus, where N(4S) is generated by photodecomposition of NO by 193 nm laser radiation behind reflected shock waves. The rate constant of the reaction, N + NO-->N2 + O (1) has been determined using pseudo first-order kinetic analysis to be k1 = (1.3 +/- 0.3) X 10(13) (cm3 mol-1 s-1) over 1600-2300 K temperature range, which agrees very well with the estimation by Baulch et al. [Evaluated Kinetic Data for High Temperature Reactions (Butterworths, London, 1973), Vol. 2]. No (or very small) activation energy of this process was confirmed. Also, the rate constant of the reaction, N + H2-->NH + H (2) has been decided by adding H2 to NO-Ar mixtures; it is k2 = (2.8 +/- 0.2) X 10(14) exp(- Ea/RT) (cm3 mol-1 s-1), where Ea = 33 +/- 7 kcal/mol. A quantum mechanical calculation performed in order to determine the mechanism of this reaction suggests that the reaction N(4S) + H2-->NH + H proceeds via a direct abstraction of H atom from H2, and it gives calculated activation energy which is in good agreement with the present experiment.