Shock tube measurements of the reactions of CN with O and O 2

The rate coefficients of the reactionsandwere determined in a series of shock tube experiments from CN time histories recorded using a narrow‐linewidth cw laser absorption technique. The ring dye laser source generated 388.44 nm radiation corresponding to the CN B 2 Σ + ( v = 0) ← X 2 Σ + ( v = 0) P‐branch bandhead, enabling 0.1 ppm detection sensitivity. Reaction (1) was measured in shock‐heated gas mixtures of typically 200 ppm N 2 O and 10 ppm C 2 N 2 in argon in the temperature range 3000 to 4500 K and at pressures between 0.45 and 0.90 atm. k 1 was determined using pseudo‐first order kinetics and was found to be 7.7 × 10 13 (±20%) [cm 3 mol −1 s −1 ]. This value is significantly higher than reported by earlier workers. Reaction (2) was measured in two regimes. In the first, nominal gas mixtures of 500 ppm O 2 and 10 ppm C 2 N 2 in argon were shock heated in the temperature range 2700 K to 3800 K and at pressures between 0.62 and 1.05 atm. k 2 was determined by fitting the measured CN profiles with a detailed mechanism. In the second regime, gas mixtures of 500 ppm O 2 and 1000 ppm C 2 N 2 in argon were shock heated in the temperature range 1550 to 1950 K and at pressures between 1.19 and 1.57 atm. Using pulsed radiation from an ArF excimer laser at 193 nm, a fraction of the C 2 N 2 was photolyzed to produce CN. Pseudo‐first order kinetics were used to determine k 2 . Combining the results from both regimes, k 2 was found to be 1.0 × 10 13 (±20%) [cm 3 mol −1 s −1 ].