A shock tube study of the reactions of CN and NCO with NO2

Abstract

The total rate coefficients for the reactions C N + N O 2 → p r o d u c t s (1) N C O + N O 2 → p r o d u c t s (2)were measured at temperatures between 1000 and 1600 K and pressures near 1.4 atm in a shock tube. Narrow-line laser absorption was utilized to record time histories of CN and NCO radicals in C2N2/NO2/Ar laser photolysis experiments. In the experiment, CN production is nearly instantaneous via photolysis of C2N2; production of NCO radicals follows from the main product channel of reaction (1). A least-squares fit to the results for reaction (1) is given by the expression k 1 = 1.59 × 10 13 exp ⁡ ( 570 / T [ K ] ) c m 3 m o l − 1 s − 1 with corresponding uncertainty factors of f=0.91 and F=1.09 at the low-temperature extreme; f=0.84 and F=1.17 result at the high-temperature extreme. The uncertainty factors give the limiting values of the rate coefficient: kmin=fkbest fit, {itkmax=Fkbest fit. The rate coefficient of reaction (2) was measured as k2=4.5×1012 cm3 mol−1 s−1 (f=0.75, F=1.27) for temperatures near 1250 K. Incorporating the data from the present study with the results from lower-temperature studies gives the following empirical expressions for the total rate coefficients valid for temperatures ranging from 300 to 1600 K: k 1 = 6.16 × 10 15 T [ K ] − 0.752 exp ⁡ ( − 173 / T [ K ] c m 3 m o l − 1 s − 1 k 2 = 3.25 × 10 12 exp ⁡ ( 356 / T [ K ] ) c m 3 m o l − 1 s − 1 .