Wavelength Dependence of UV Photoemission from Solvated Electrons in Bulk Water, Methanol, and Ethanol

We have measured the wavelength dependence (340–215 nm) of one-photon photoemission from the ground electronic state of solvated electrons in bulk water, methanol, and ethanol. In every case, the vertical electron binding energy (VBE) gradually increased with photon energy, indicating that the photoelectron kinetic energy diminishes as a result of electron–vibration inelastic scattering prior to emission from the liquid surface. In contrast, the VBE of the Rydberg electron in DABCO (1,4-diazabicyclo­[2,2,2]­octane), which has a surface-excess density, revealed no clear wavelength dependence. These results suggest that the solvated electrons are created predominantly in the bulk and that VBEs measured using UV photoemission spectroscopy of liquids generally require energy corrections to account for inelastic scattering effects. From the wavelength dependence, we have re-estimated the VBEs of solvated electrons in bulk water, methanol, and ethanol to be 3.3, 3.1, and 3.1 eV, respectively. Hydrated electrons were also identified by photoemission spectroscopy using 90 nm radiation.