Femtosecond studies of electrons in liquids

Abstract

Femtosecond time-resolved measurements were performed on the geminate recombination and solvation of electrons in liquids. The electrons were generated by multiphoton ionization in neat water and alkanes and by multiphoton detachment from Cl− and OH− ions in aqueous solution. For the neat liquids, the results are compared with the Onsager model of ion-pair recombination. An isotope effect is observed in the dynamics of both solvation and recombination in neat D2O relative to H2O. Studies with improved time resolution of electron solvation in neat water have measured the formation, decay, and absorption spectrum of the wet electron, i.e., the presolvated electron. By the discovery of an isosbestic wavelength, the formation of the wet electron is shown to involve two states; i.e., the transition is not continuous. The picture of the wet electron as an excited state of the solvated electron is presented. The differences in the solvation dynamics of electrons that are generated from neat water and from OH− and Cl− ions show that short-range molecular effects are important.