Nanosecond kinetics of hydrated electrons upon water photolysis by high intensity femtosecond UV pulses

We report a nanosecond laser study of the transient absorption of hydrated electrons generated by multiphoton ionisation of liquid water upon excitation at 266 and 400 nm by femtosecond pulses with power densities higher than 1 TW/cm2. For both wavelengths, as the pump power density increases, the signal amplitude increases and the decay becomes faster proving that more electrons are produced. However, we show that in the nanosecond time range, under pump power densities higher than 1 TW/cm2, the distribution of the hydrated electrons is not uniform along the optical pathway of the pump beam in the water sample.