Observation of a persistent infrared absorption following two photon ionization of liquid water

Photo-ionization of water following absorption of two photons at 6.2 eV (200 nm) is studied by femtosecond transient absorption spectroscopy. After the first few picoseconds, the spectrum resembles that of the equilibrated hydrated electron but additionally exhibits a persistent induced absorption in the infrared. The spectral shape stays the same for more than 300 ps. The persistent infrared absorption is induced by two photon absorption and its dynamics is similar to that of the visible absorption pertaining to the hydrated electron. Our observations suggest that the persistent infrared absorption is related to the presence of the hydrated electron.