A direct measurement of the reaction NH3 + NH→2NH2

The reaction of NH in its electronic ground state with ammonia was investigated behind incident shock waves using narrow line width absorption detection of NH(X3Σ−). The initial concentrations of HN3 which was used as source of NH(X3Σ−) were very low in order to reduce the influence of secondary reactions. Thus it became possible to measure kinetic data for the reaction of NH(X3Σ−) + NH3 (1) directly. In a temperature range from 1300 to 1700 K a rate constant k1 = 10(14.5±0.3)exp (–(112±9)kJ mol−1/RT)cm3/mol s was obtained. The apparent energy of activation fits well into an Evans Polanyi plot for H abstraction reactions of NH(X3Σ−).