  We report the first observation of intermolecular Coulombic decay (ICD) in
liquid water following inner-valence ionization. By combining a monochromatized
table-top high-harmonic source with a liquid micro-jet, we recorded
electron-electron coincidence spectra at two photon energies that identify the
ICD electrons, together with the photoelectrons originating from the 2a1
inner-valence band of liquid water. Our results confirm the importance of ICD
as a source of low-energy electrons in bulk liquid water and provide
quantitative results for modeling the velocity distribution of the slow
electrons that are thought to dominate radiation damage in aqueous
environments.
