The heat of formation of N₂H₂ and the proton affinity of N₂

Measurements of the heat of formation of N 2 H 2 from the appearance potential for m/e 30 ions from N 2 H 4 give irreproducible results. Using N 2 H 2 , reproducible values for the appearance potentials of m/e 30, 29, and 28 ions were obtained. These values yield an ionization potential of N 2 H 2 , IP(N 2 H 2 ) = 9.7 ± 0.1 V, a heat of formation of N 2 H 2 , ΔH f (N 2 H 2 ) = 36 ± 2 kcal/mol and a proton affinity of N 2 , PA(N 2 ) = 5.6 eV. An estimate of the ionization potential of N 2 H radical, IP(N 2 H) = 7.6 V, was also obtained.