Solvent effects on geminate recombination dynamics after photodetachment

The time-dependent survival probability for photoelectrons produced following resonant excitation of I− in its first charge-transfer-to-solvent (CTTS) band is determined by femtosecond pump-probe spectroscopy. The solvent effect on localization and recombination dynamics of the detached solvated electrons in various hydroxylic solvents (H2O, CH3OH, C2H5OH, C3H7OH, C4H9OH) is studied. The data are consistent with a caged geminate pair being formed in the CTTS photodetachment step. In all solvents, the geminate recombination of the detached electron can be modeled as competition between diffusive escape from an attractive short-range potential (∼3kBT) and reverse electron transfer to reform ground state iodide.