Femtosecond solvation dynamics of solvated electrons in neat water

We report on transient pump-probe spectroscopy of equilibrated solvated electrons in neat water in the visible/near-infrared using femtosecond pulses and polarization resolution. By excitation in the blue wing of the absorption band the e^- are promoted from the 1s ground state to the highest of the 2p sub-states. First rapid solvent relaxation and/or population redistribution among the excited 2p sub-states is followed by the population of a modified excited state p′ with a lifetime of τ₂=190±40 fs. The second intermediate is assigned to a modified ground state s′′ while subsequent ground state recovery proceeds within τ₃=0.9±0.15 ps. The negligible net anisotropy <0.01 of the probe absorption indicates that the observed distribution of solvent cavities of hydrated electrons is close to spherical symmetry.