Kinetics of the O(P-3)+N2O reaction. 2. Interpretation and recommended rate coefficients

The reaction O(P-3) + N2O is important to models of NOx pollutant and prope llant chemistry and to the understanding of the thermal decomposition of N2 O, which has historically played a key role in the development of unimolecu lar reaction theory. The reaction has two important product channels: O + N 2O --> NO + NO (Delta H-0 = -36 kcal/mol) (R1); O + N2O --> O-2 + Nz (Delta H-0 = -79 kcal/mol) (R2). Rate coefficients of these reactions have been t he subject of several reviews. However, clear reasons why many of the evalu ated, nonretained data differ from recommendations have not previously been known. There has been a great deal of controversy over the rate coefficien ts, particularly for reaction R2. Here, the relevant data are critically ev aluated using detailed chemical modeling as an important tool. The results explain many of the discrepancies. Some of the data of central importance i n earlier evaluations are shown to be incorrect. Additionally, some importa nt features of the global behavior of the mixtures studied, which had previ ously not been understood, are explained, and the possible effects of hypot hetical H2O contamination on N2O shock tube studies was quantitatively inve stigated. It is shown that the bulk of the rate coefficient results remaini ng after the evaluations can be combined with the intermediate temperature results for k(tot) = k(1) + k(2) from FGFAM (Fontijn, A.; Goumri, A.; Ferna ndez, A.; Anderson, W. R.; Meagher, N. E. J. Phys. Chem., preceding paper i n this issue) to obtain fitted recommendations: k(1) = 1.52 x 10(-10) exp(- 13 930/T) cm(3) molecule(-1) s(-1) (1370-4080 K); k(2) = 6.13 x 10(-12) exp (-8,020/T) cm(3) molecule(-1) s(-1) (1075-3340 K). Until recently, it was b elieved rate coefficients of the two product channels were approximately eq ual over a very wide temperature range. In contrast, the present study has led to the conclusion that reaction R2 dominates below, and reaction R1 abo ve, 1840 K.