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Cations Strongly Reduce Electron-Hopping Rates in Aqueous Solutions

Ottosson, Niklas; Odelius, Michael; Spangberg, Daniel; Pokapanich, Wandared; Svanqvist, Mattias; Öhrwall, Gunnar LU ; Winter, Bernd and Bjorneholm, Olle (2011) In Journal of the American Chemical Society 133(34). p.13489-13495
Abstract
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 MgBr2 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... (More)
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 MgBr2 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. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Journal of the American Chemical Society
volume
133
issue
34
pages
13489 - 13495
publisher
The American Chemical Society
external identifiers
  • wos:000295551600049
  • scopus:80052081471
ISSN
1520-5126
DOI
10.1021/ja204100j
language
English
LU publication?
yes
id
ed415467-2d2b-423a-9e74-cd70362f605f (old id 2208199)
date added to LUP
2011-11-28 09:37:06
date last changed
2017-10-08 03:49:47
@article{ed415467-2d2b-423a-9e74-cd70362f605f,
  abstract     = {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 MgBr2 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.},
  author       = {Ottosson, Niklas and Odelius, Michael and Spangberg, Daniel and Pokapanich, Wandared and Svanqvist, Mattias and Öhrwall, Gunnar and Winter, Bernd and Bjorneholm, Olle},
  issn         = {1520-5126},
  language     = {eng},
  number       = {34},
  pages        = {13489--13495},
  publisher    = {The American Chemical Society},
  series       = {Journal of the American Chemical Society},
  title        = {Cations Strongly Reduce Electron-Hopping Rates in Aqueous Solutions},
  url          = {http://dx.doi.org/10.1021/ja204100j},
  volume       = {133},
  year         = {2011},
}