Ultrafast spectroscopic study on charge-transfer reactions in condensed phase
Ultrafast femtosecond spectroscopic investigations on the dynamics of electron transfer in the solution phase have been performed. The chemical systems selected for the studies are the hydrated electron and a ruthenium mixedvalence compound. The hydrated electron has been a prototypical system for investigating many dynamical processes in the solution phase, such as solvation, non-adiabatic electronic relaxation and charge transfer reaction. In the present study, pump-probe spectroscopy has been employed to investigate structural and chemical properties of the optically excited states of the hydrated electron. Measurement of spatial extent of the wavefunction and kinetics of the electron transfer scavenging of the excited states is discussed. The electron transfer in a mixed-valence metal compound is an important system, in which the charge transfer process is strongly coupled to both the intramolecular and solvent nuclear degrees of freedom. Here, investigations on the dynamics of back electron transfer after the optical excitation and subsequent energy relaxation on intramolecular and solvent nuclear coordinates are described.