Regensburg 2004 – wissenschaftliches Programm

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O: Oberflächenphysik

O 6: Struktur und Dynamik reiner Oberflächen

O 6.3: Vortrag

Montag, 8. März 2004, 11:45–12:00, H45

X-ray reflectivity study of the aqueous solution-gas interface — •Michael Paulus, Michael Sprung, Christian Gutt, and Metin Tolan — Experimentelle Physik I, Universität Dortmund, 44221 Dortmund

Interfacial properties of aqueous salt solutions are important in many biological and geological systems.e.g. for the reactivity of sea salt aerosols in the marine boundary layer.

In the past a large number of theoretical work has been performed to study the liquid - gas interface of aqueous alkali halide electrolyte solutions. Molecular dynamics simulations revealed a partial ion enrichement of alkali halides solution close to the liquid-gas interface. This finding is in contrast to expectations based on classical electrostatic calculations. It has been reported that this effect is most prominent if sodium iodide is used as the electrolyte. The expected thickness of the ion enriched region is of the order of 1nm.

We report on x-ray reflectivity experiments of aqueous solutions of sodium iodine of different concentrations. The experiments provided for the first time a detailed picture of the electron density profile of aqueous salt solutions close to the liquid-gas interface. In contrast to the results of molecular dynamic simulations, we observed for all investigated concentrations a water enriched region of thickness 1-2 nm at the surface.