부산대학교 도서관

We study how the ultrafast intermolecular hopping of electrons excited from the water Ols core level into unoccupied orbitals depends on the local molecular environment in liquid water. Our probe is the resonant Auger decay of the water Ols core hole (lifetime ~-~3.6 fs), by which we show that the electronhopping rate can be significantly reduced when a first-shell water molecule is replaced by an atomic ion. Decays resulting from excitations at the Ols post-edge feature (∼S4O eV) of 6 m LiBr and 3 m MgBr2 aqueous solutions reveal electronhopping times of ∼1.S and 1.9 fs, respectively; the latter represents a 4-fold increase compared to the corresponding value in neat water. The slower electron-hopping in electrolytes, which shows a strong dependence on the charge of the cations, can be explained by ion-induced reduction of water-water orbital mixing. Density functional theory electronic structure calculations of solvation geometries obtained from molecular dynamics simulations reveal that this phenomenon largely arises from electrostatic perturbations of the solvating water molecules by the solvated ions. Our results demonstrate that it is possible to deliberately manipulate the rate of charge transfer via electron-hopping in aqueous media. [ABSTRACT FROM AUTHOR]