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+.