Infrared spectra of the cluster ions H7O⁺₃·H2 and H9O⁺₄·H2

Abstract

Infrared spectra of hydrated hydronium ions weakly bound to an H2 molecule, specifically H7O ⁺ ₃ ·H2 and H9O ⁺ ₄ ·H2, have been observed. Mass-selected parent ions, trapped in a radio frequency ion trap, are excited by a tunable infrared laser; following absorption, the complex predissociates with loss of the H2, and the resulting fragment ions are detected. Spectra have been taken from 3000 to 4000 cm^−1, with a resolution of 1.2 cm^−1. They are compared to recent theoretical and experimental spectra of the hydronium ion hydrates alone. Binding an H2 molecule to these clusters should only weakly perturb their vibrations; if so, our spectra should be similar to spectra of the hydrated hydronium ions H7O ⁺ ₃ and H9O ⁺ ₄.

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