High temperature study of the reactions of O and OH with NH₃

Abstract

Abstract Mixtures of NH 3 and N 2 O dilute in Ar were heated behind incident shock waves in the temperature range 1750–2060 K. A cw ring dye laser, tuned to the center of an OH absorption line in the ultraviolet, was used to monitor OH concentration profiles by absorption spectroscopy. Infrared emission was used to follow N 2 O (at 4.5 μm) and NH 3 (at 10.5 μm) concentration—time histories. The early‐time NH 3 and OH concentration profiles were sensitive to the rate constants of the reactions magnified image leading to the following best‐fit expressions for k 2 and k 3 : k 2 = 10 13.34±0.3 exp(−4470/ T ) and k 3 = 10 13.91±0.2 exp(‐4230/ T ) cm 3 mol −1 s −1 . The results of this study combined with previous low‐temperature data suggest a significant non‐Arrhenius behavior for both k 2 and k 3 .