Reactions of Nitrogen—Hydrogen Radicals. II. Decomposition of Hydrazine by Hydrogen Atoms

The luminescent reaction of hydrazine with atomic hydrogen was studied in flowing gas systems. The emission is due to NH2 radicals apparently produced by the process N2H4+H→NH3+NH2(2A1)* . Estimates of the emission quantum yield show that this is a relatively minor process. Accepting the conclusion of Schiavello and Volpi that the major decomposition process is N2H4+H→N2H3+H2 with a rate, 3.5×108 exp (−2000/RT) liters/mole·sec, the temperature dependence of the emission intensity is interpreted in terms of these competing processes to give a rate 1.2×105 exp (−2600/RT) liters/mole·sec for the emission reaction. The emission spectrum appears to have a short wavelength limit corresponding to 50.7 kcal, yielding a value for the heat of formation of NH2 consistent with other determinations. The absorption spectrum shows an unexpectedly high concentration of NH2 radicals in the reaction zone. This is consistent with the other known facts if the process, N2H3+H→2NH2, becomes important when the [H]/[N2H4] ratio is large.