Dresden 2006 – wissenschaftliches Programm

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O: Oberflächenphysik

O 29: Poster session II (Nanostructures, Magnetism, Particles and clusters, Scanning probe techniques, Time-resolved spectroscopy, Structure and dynamics, Semiconductor surfaces and interfaces, Oxides and insulators, Solid-liquid interfaces)

O 29.78: Poster

Mittwoch, 29. März 2006, 14:30–17:30, P2

Segregation of salt ions at surfaces of polar liquids and the corresponding amorphous solids — •O. Höfft¹, U. Kahnert¹, V. Kempter¹, P. Jungwirth², and L.X. Dang³ — ¹Institut für Physik und Physikalische Technologien, TU Clausthal, Leibnizstr. 4 38678 Clausthal-Zellerfeld — ²Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Prague — ³EMSL, Pacific Northwest National Lab

Surface segregation of iodide, but not of fluoride, or cesium, is observed by a combination of metastable impact electron spectroscopy (MIES) and ultraviolet photoelectron spectroscopy (UPS(HeI)) of amorphous solid water exposed to CsI and NaI on one side and NaF and CsF vapour on the other side. The same surface ionic behavior is also derived from molecular dynamics (MD) simulations of the analogous aqueous salt solutions. These results give a strong support to the suggested surface propensity of heavier halides (iodide, bromide) in water and confirm the structural similarity between the amorphous solid and the corresponding liquid. In contrast, no appreciable surface segregation of ions is observed in methanol, neither in the experiment nor in the simulation, which points to the remarkable surface properties of water among polar solvents. The propensity of heavier halides for the air/solution interface has important implications for heterogeneous chemical processes, particularly in the atmosphere.