Shock tube measurements of the reactions of CN with O and O2

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Abstract
The rate coefficients of the reactions equation image and equation image were 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 B2Σ+(v= 0) ←X2Σ+(v= 0) P‐branch bandhead, enabling 0.1 ppm detection sensitivity.Reaction (1) was measured in shock‐heated gas mixtures of typically 200 ppm N2O and 10 ppm C2N2in argon in the temperature range 3000 to 4500 K and at pressures between 0.45 and 0.90 atm.k1was determined using pseudo‐first order kinetics and was found to be 7.7 × 1013(±20%) [cm3mol−1s−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 O2and 10 ppm C2N2in argon were shock heated in the temperature range 2700 K to 3800 K and at pressures between 0.62 and 1.05 atm.k2was determined by fitting the measured CN profiles with a detailed mechanism. In the second regime, gas mixtures of 500 ppm O2and 1000 ppm C2N2in 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 C2N2was photolyzed to produce CN. Pseudo‐first order kinetics were used to determinek2. Combining the results from both regimes,k2was found to be 1.0 × 1013(±20%) [cm3mol−1s−1].

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