Vacuum-Ultraviolet Photochemistry. VII. Photolysis of Hydrazine at 1236 and 1470 Å

The photolysis of hydrazine vapor has been investigated at 1236 and 1470 Å. At 1236 Å, fluorescence is observed at 3360 Å and is attributed to the NH(A³π→X³Σ⁻) transition. The emission has been studied as a function of pressure and photolysis time. No emissions were observed at 1470 Å. The products of the photolysis of hydrazine are nitrogen, hydrogen, and ammonia. The pressure dependence of these products has been determined at 1236 and 1470 Å. Formation of the parent ion N₂H₄⁺ probably occurs at 1236 Å but not at 1470 Å. At the latter wavelength, reduction of the hydrogen yield upon addition of C₂D₄ is explained by the reactions: $$\begin{array}{c}{\mathrm{N}}_2{\mathrm{H}}_4\mathrm{+hv\to }{\mathrm{N}}_2{\mathrm{H}}_3+\mathrm{H},\\ \mathrm{H}+{\mathrm{N}}_2{\mathrm{H}}_4\to {\mathrm{H}}_2+{\mathrm{N}}_2{\mathrm{H}}_3.\end{array}$$ Nitrogen production is not reduced in the presence of C₂D₄ and the quantum yields of hydrogen and nitrogen are equal under these conditions. These products arise mainly from decomposition of N₂H₂ (di‐imide). The latter may be formed directly from hydrazine, from decomposition of N₂H₃ or in the disproportionation of N₂H₃ radicals. Contributions from radical—radical combination reactions are minor based on the relative H₂/N₂ yields observed in this study and on the lack of mixing of isotopic nitrogen previously reported.