The reactions of N,O with NO and OH radicals have been studied using ab initio molecular orbital theory The energetics and molecular parameters, calculated by the modified Gaussian-2 method ( G 2 M ) . have been used to compute the reaction rate constants on the basis of the TST and RRKM theories The reaction N,O + NO -N, + NO, ( 1 1 was found to proceed by direct oxygen abstraction and to have a barrier of 47 kcal/mol. The theoretical rate constant. k , = 8 74 X X T'23 exp (-23.292R) crn3 molecule-' s-'. is in close agreement with earlier estimates. The reaction of N,O with OH at low temperatures and atmospheric pressure is slow and dominated by association, resulting in the HONNO intermediate. The calculated rate constant For 300 K 5 T 5 500 K is lower by a few orders than the upper limits previously reported in the literature. At temperatures higher than 1000 K , the N,O + OH reaction is dominated by the N, + OzH channel, while the HNO + NO channel is slower by 2 -3 orders of magnitude The calculated rate constants at the temperature range of 1000-5000 K for N,O + OH -N2 + 0 , H (2A) and N,O + OH + HNO + N O ( 2 8 ) are fitted by t h e following expressions k2, = 2 I5 X 10-'' X T4" X exp ( -18.400R).
k,, = I96 X lo-," X T333 X exp (-12.623Rl. in units of cm3 molecule-' s-' Both N,O + NO and N,O + OH reactions are confirmed to enhance, albeit inefficiently. the N,O decomposition by reducing its activation energy o 1996 lohn Wiley & Sons, Inc