Ionization potential of the NH free radical by mass spectrometry: Production of ground state and electronically excited NH by F-atom reactions

Sequential F-atom reactions with ammonia were used to produce NH radicals in the X 3Σ− ground state and the a 1Δ excited state. Ionization potential measurements on both of these species lead to the determination I(NH) = 13.47±0.05 eV, indicating that the error limits in at least one of the previous studies was seriously underestimated. The F-atom reactions also produced ground and electronically excited N atoms. Efforts to obtain an independent measurement of the heat of formation of NH using dissociative ionization of NH3 were unsuccessful, apparently because of excess energy involved in the ionization process. Some important N–N and N–H bond dissociation energies have been updated.