Infrared spectrum of the NH4-dn+ cation trapped in solid neon

Abstract

The NH₄⁺ cation has been stabilized in solid neon in sufficient concentration for the identification of both of its infrared-active vibrational fundamentals, which appear within a few wavenumbers of the gas-phase band centers. Systematic alteration of the concentrations and positions of introduction of NH₃ and H₂ in the discharge sampling experiments demonstrated that the highest yield of NH₄⁺ resulted when both the NH₃ and the H₂ were introduced downstream from a discharge through pure neon. In this configuration, each of these molecules can be ionized by excited neon atoms and their resonance radiation (16.6 eV to 16.85 eV), but fragmentation is minimized. Both infrared-active vibrational fundamentals of ND₄⁺ and several fundamentals of each of the partially deuterium-substituted isotopomers of NH₄⁺ were also identified. Evidence is presented for complexation of NH₄⁺ with an H atom or with one or more H₂ molecules.