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Phys. Rev. Lett. 99, 086105 (2007) [4 pages]

Specific Ion Adsorption and Short-Range Interactions at the Air Aqueous Solution Interface

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Viswanath Padmanabhan*, Jean Daillant†, and Luc Belloni
Laboratoire Interdisciplinaire sur l’Organisation Nanométrique et Supramoléculaire, SCM, bât. 125, CEA Saclay, F-91191 Gif-sur-Yvette Cedex, France

Serge Mora
UMR 5587 CNRS, Université Montpellier II, place Eugène Bataillon, F-34095 Montpellier Cedex 5, France

Michel Alba
Direction des Sciences de la Matière, CEA Saclay, F-91191 Gif-sur-Yvette Cedex, France

Oleg Konovalov
ESRF, 6 rue Jules Horowitz, B.P. 220, 38043 Grenoble Cedex, France

Received 14 April 2007; published 24 August 2007

We have investigated the surface composition of alkali-halide aqueous solutions using grazing incidence x-ray fluorescence. Using mixtures of salts as a means to enhance the short-range effects, small differences in concentration over a few angstrom could be resolved, with, for example I- or Br->Cl-. In order to explain our data, we need to include an effective potential accounting for the short-range (Å) solvent mediated couplings, responsible for specific effects together with dispersion forces. This attractive potential (few kBT for halides) leads to concentration profiles which are in good agreement with recent numerical simulations.

© 2007 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevLett.99.086105
DOI:
10.1103/PhysRevLett.99.086105
PACS:
68.03.Cd, 61.10.Kw, 61.20.−p

*Present address: Max Planck Institute of Colloids and Interfaces, Wissenschaftspark Golm, D-14424 Potsdam, Germany.

†jean.daillant@cea.fr

 
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