Dynamics of a photoexcited hydrated electron

Combining photon-echo and frequency-resolved pump-probe techniques with extremely short laser pulses that consist of only few optical cycles, we investigate the dynamics of the equilibrated hydrated electron. The pure dephasing time of the hydrated electron deduced from the photon-echo measurements is approximately 1.7 fs. The shape of the absorption spectrum is excellently described by an extended Lorentzian contour which spectral width is fully determined by the pure dephasing time. The experimental data is successfully described with a model in which the excited state lifetime is approximately 50 fs in water and approximately 70 fs in heavy water. The deuteration effect on the lifetime strongly suggests that OH(OD)-vibrational modes in the first solvation shell act as accepting modes for the energy relaxation.