Gas phase infrared spectra of oxonium hydrate ions from 2 to 5 μ

Infrared spectra of oxonium hydrate ions, generated by pulse radiolysis of argon containing small amounts of water vapor, have been measured using a signal averaging technique. The symmetric and antisymmetric OH stretch frequencies of the H₃O⁺ part of H₉O₄⁺ are found at 3000 and 2660 cm^-1. H₁₁O₅⁺ frequencies are found at 2180, 2860, and 3200 cm^-1. In addition, bands at 3620 and 3710 cm^-1, due to the outer water molecules are observed. Bands found during the growth of H₉O₄⁺ at low water pressures are at 3490, 3290, 3170, 2850, and 2700 cm^-1. The 3490 cm^-1 frequency is attributed to H₃O⁺.