Cations Strongly Reduce Electron-Hopping Rates in Aqueous Solutions
2011 (English)In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 133, no 34, 13489-13495 p.Article in journal (Refereed) Published
We study how the ultrafast intermolecular hopping of electrons excited from the water O1s core level into unoccupied orbitals depends on the local molecular environment in liquid water. Our probe is the resonant Auger decay of the water O1s core hole (lifetime similar to 3.6 fs), by which we show that the electron-hopping rate can be significantly reduced when a first-shell water molecule is replaced by an atomic ion. Decays resulting from excitations at the O1s post-edge feature (similar to 540 eV) of 6 m LiBr and 3 m MgBr(2) aqueous solutions reveal electron-hopping times of similar to 1.5 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.
Place, publisher, year, edition, pages
2011. Vol. 133, no 34, 13489-13495 p.
IdentifiersURN: urn:nbn:se:su:diva-68041DOI: 10.1021/ja204100jISI: 000295551600049OAI: oai:DiVA.org:su-68041DiVA: diva2:471805
authorCount :82012-01-032012-01-022012-01-03Bibliographically approved