The Ionization and Dissociation of Water Vapor and Ammonia by Electron Impact

The results of a mass-spectrometric study of the products of ionization and dissociation of water vapor and ammonia by electron impact are given. The ionizing potential of the H₂O molecule is found to be 13.0±{}0.2 volts, and of the NH₃ molecule 10.5±{}0.1 volts. The possible processes responsible for the formation of the various ions observed, both positive and negative, are discussed. Ions observed in H₂O vapor are H₂{O}⁺$, O${H}⁺$, ${O}⁺$, ${H}⁺$, $H₂⁺$, ${H}₃O⁺, O^-, and H^-. Ions observed in NH₃ are NH₃⁺, NH₂⁺, NH⁺, N⁺, H⁺, NH₃⁺⁺, NH₂^-, and H^-.