Pairwise Recombination in the Decay of Photochemical Hydrated Electrons*

The decays of hydrated electrons generated by 265 nm laser flash photolysis of aqueous I ‐ , tyrosine, tryptophan, lysozyrne. and ribonuclease have been analyzed by numerical computing. Homogeneous reactions do not explain the data without e ‐ aq —radical back reactions significantly faster than diffusion limited. The results are explained by postulating pairwise recombination persists at times where conventional diffusion theory predicts randomization, particularly at low intensities and in the absence of effective e ‐ aq scavengers. The physical mechanisms responsible for these effects are considered.