Electron propagator study of the excitation spectrum of the solvated hydronium radical

Abstract

In an ab initio MCSCF study, the hydronium H3O. radical has been hydrated within a spherical dielectric cavity of various radii, while using both the static and optical dielectric constants of water. The electronic excitation spectrum was computed with the help of a 2-particles propagator method. The effect of non specific solvation is an overall red shift, absorbing transitions at 1.8 eV and 2.4 eV are predicted. The resulting apparent absorption spectrum of the hydrated H3O radical looks similar to the spectrum of the "hydrated electron" (e-)aq. However, an absorption band of the first excited state (H3O.)*aq is estimated to be centered around 1.50 eV. We perform a comparative analysis of this band with the 1.45 eV band observed within femtosecond spectroscopy experiments. An "itinerant radical model" of the hydrated electron is also briefly discussed.