KINETIC-STUDIES OF THE REACTIONS OF NCO RADICALS WITH NO AND O2 IN THE TEMPERATURE-RANGE BETWEEN 294-K AND 1260-K

Absolute rate coefficients for the reaction of NCO radicals with NO were measured in the temperature range between 294 and 1260 K and the pressure range between 6 and 170 Torr in a heatable quartz reactor by means of the laser photolysis/laser-induced fluorescence technique. NCO radicals were produced in the fast reaction of CN radicals with O2. CN was generated by 193 nm photolysis of cyanogen. A curved Arrhenius plot of the rate constant was found with a negative temperature dependence. The data were fitted to the expression k1(T) = (3.0 +/- 0.4) x 10(17) T(-1.53 +/- 0.1) exp [(-260 +/- 30) K/T] cm3 mol-1 s-1. No pressure dependence was found between 6 and 73 Torr. An upper limit of the rate constant for the reaction of NCO radicals with O2 was measured to be 3 x 10(9) cm3 mol-1 s-1 at 1260 K.