Dynamics of solvated electrons in polar liquids using 2-eV femtosecond laser pulses

The multiphoton ionization of liquid water and methanol and the dynamics of electron solvation in those media are studied with femtosecond time-resolved spectroscopy using a 2- eV laser light pump beam. The formation of the solvated electron in methanol is probed for the first time with femtosecond time resolution. The absorbance A is measured as function of the laser irradiance E for both water and methanol. The power law A varies direct as Ex obtained for water (x equals 1.8) and for methanol (x equals 1.9) differs markedly from that expected from energetic considerations. This is explained in terms of a resonant contribution of intermediate electronic states in the multiphotonic ionization.