Temperature dependent relaxation and recombination dynamics of the hydrated electron

The ultrafast solvation and recombination dynamics of the hydrated electron generated by two-photon ionization of water at 4.65 eV is studied by trans ient absorption spectroscopy as a function of temperature in the range from 277 K to 355 K. The part of the spectral blue shift which is observed in t he absorption spectrum of the hydrated electron after 1 ps is purely contin uous and is accurately described by the well known analytical expression fo r the temperature dependent absorption spectrum of the ground state hydrate d electron. This indicates that thermal relaxation or more likely solvation of the hydrated electron predominantly causes the blue shift. The survival probability of the hydrated electron shows a strong temperature dependence , which is satisfactory explained by the temperature dependent mobility and reaction rates of the species involved in the recombination. This implies that the average initial separation between the hydrated electron and the i onization site of [r(0)]=1.0 +/- 0.1 nm does not depend significantly on th e bulk water temperature. (C) 2000 American Institute of Physics. [S0021-96 06(00)50927-1].