High temperature determination of the rate coefficient for the reaction H2O + CN → HCN + OH

The rate coefficient, k, of the reaction has been determined in the temperature range 2460–2840 K using a shock tube technique. C₂N₂? H₂O? Ar mixtures were heated behind incident shock waves and the CN and OH concentration time histories were monitored simultaneously using broad-band absorption near 388 nm (CN) and narrow-line laser absorption at 306.67 nm (OH). The rate coefficient expression providing the best fit to the data was with uncertainty limits of about ±45% in the temperature range 2460–2840 K. The rate coefficient of the reverse reaction was calculated using detailed balancing, and its extrapolation to lower temperatures was compared with previously published results.