The product branching ratio of NH2 + NO → NNH + OH and NH2 + NO → N2 + H2O has been determined in the temperature range 1826-2159 K in a shock tube study. The pressure range behind reflected shock waves was 1.10 to 1.21 bar. The time history of the NH2 radical was measured using a frequency modulation absorption technique. The initial gas mixture compositions were 8-28 ppm monomethylamine (CH3NH2), 0.4-1.2% ammonia (NH3), and 0.4% NO, and the balance Ar. According to sensitivity analysis using a detailed 125-reaction mechanism, the NH2 profiles are mainly sensitive to the branching ratio α = k1a/(k1a + k1b) under the experimental conditions of this study, and they exhibit only a small sensitivity to secondary reactions and the overall rate coefficient, k1 = k1a + k1b. The branching ratio increases from 0.59 ± 0.02 at 1826 K to 0.66 ± 0.04 at 2159 K. These results are consistent with our earlier measurements of the branching ratio at lower temperature and agree with the theoretical result of Miller and Klippenstein.
All Science Journal Classification (ASJC) codes
- Physical and Theoretical Chemistry