A b i n i t i o study of the energetics of the spin-allowed and spin-forbidden decomposition of HN3

Abstract

We describe an investigation of the energetics of the dissociation of ground state hydrazoic acid HN₃. The study is limited to the lowest energy spin‐allowed and spin‐forbidden decomposition pathways, namely HN₃(X̃ ¹A’)→N₂(X ¹Σ_g⁺) +NH(a ¹Δ,X ³Σ⁻) and HN₃(X̃ ¹A’) →N₃(X̃ ²Π_g)+H(²S). Complete active space SCF and multireference configuration interaction calculations with large basis sets are used (a) to determine the NNN–H and NN–NH bond dissociation energies of HN₃, (b) to locate the geometry of the transition state for the spin‐forbidden decomposition and the corresponding activation energy, and (c) to investigate the magnitude and origin of the exit channel barrier in the spin‐allowed decomposition channel.