Kinetics of the reactions of NCO radicals with NO and NH3

The rate constants for the reaction of NCO (X(2)II) radicals with NO and NH3 were measured at 20 Torr total pressure in temperature ranges of 290-1098 K and 295-882 K, respectively, using ClNCO excimer laser photolysis for NCO radical formation in combination with laser-induced fluorescence detection of NCO. In the temperature range investigated the NCO+NO reaction exhibits a negative temperature dependence which is described by the following three parameter Arrhenius equation: k(NCO+NO)(T) = (1.45(-0.35)(+0.55)) x 10(-5) x T-(-1.98+/-0.06) x exp [-(3.74(-0.83)(+0.91))/RT] cm(3)s(-1), with E(0) in units of kJ/mol. For the NCO+NH3 reaction the measurements exhibit a positive temperature dependence over the temperature range investigated with a slight upwards curvature. A modified three parameters Arrhenius fit provides a good description of the experimental data: kNCO+NH3 (T) = (4.6(-1.8)(+1.1)) x 10(-20) x T--0.07((2.48+0.04)) x exp [-(4.1(-0.9)(+2.6))/RT] cm(3) s(-1), with E(0) in units of kJ/mol. In addition, the rate constant of the NCO+NH3 reaction was found to be pressure independent in the range 10-193 Torr at 295 K.