Direct measurements of the reaction NH2 + H2 → NH3 + H at temperatures from 1360 to 2130 K

The reaction NH2 + H2 → NH3 + H (11) was investigated behind shock waves in the temperature range from 1360 to 2130 K. Time histories of NH2 were measured by frequency modulation (FM) spectroscopy. The rate constant was determined to be k11 = 4.5 · 1013 · exp[-61 kJ mol-1/RT] cm3 mol-1 s-1 (Δlog k11 = ± 0.15, ΔEa = ±9 kJ/mol). According to recent literature values the reverse reaction NH3 + H → NH2 + H2 (-11) can be described by k-11 = 1.5 · 107 · T2.0 · exp(-47 kJ mol-1/RT) cm3 mol-1 s-1 for the temperature range of 400 to 2500 K. On the basis of k-11 and by using the enthalpy of formation of ΔfH298oK(NH2) = 190 kJ/mol, which was determined in a previous study [1], via detailed balance the following expression for the forward reaction (11) was obtained for a temperature range of 400 to 2200 K: k11 = 1.5 · 104 · T2.6 · exp(-25 kJ mol-1/ RT) cm3 mol-1 s-1. This expression is in very good agreement with the reported experimental values for k11. © by Oldenbourg Wissenschaftsverlag, München.