A PHYSICAL INTERPRETATION OF THE TIME-DEPENDENT ABSORPTION DYNAMICS OF PHOTOGENERATED ELECTRONS IN WATER

Various models for the femtosecond solvation dynamics of photogenerated electrons in water are discussed. Simulated time-dependent spectra are compared to experimental results which have been reported by Migus and co-workers. The femtosecond absorption data can be qualitatively accounted for by postulating three distinct populations of electrons which undergo solvation by different physical mechanisms: 20% are ground-state electrons which achieve equilibrium solvation within 25 fs, 25% are ground-state electrons which localize in shallow solvent traps with a lifetime of 200 fs and then exhibit a continuous shift in the absorption spectrum (τs = 200 fs) as solvation occurs, and 55% of the electrons localize in an excited state and undergo a nonadiabatic transition to the ground state with an excited-state lifetime of ≈250 fs. © 1990 American Chemical Society.