title: Surface segregation of dissolved salt ions.
abstract: Surface segregation of iodide, but not of fluoride or cesium ions, is observed by a combination of metastable impact electron spectroscopy (MIES) and ultraviolet photoelectron spectroscopy (UPS(HeI)) of amorphous solid water exposed to CsI or CsF vapor. The same surface ionic behavior is also derived from molecular dynamics (MD) simulations of the corresponding aqueous salt solutions. The MIES results show the propensity of iodide, but not fluoride, for the surface of the amorphous solid water film, providing thus strong evidence for the suggested presence of heavier halides (iodide, bromide, and to a lesser extent chloride) at the topmost layer of aqueous surfaces. In contrast, no appreciable surface segregation of ions is observed in methanol, neither in the experiment nor in the simulation. Furthermore, the present results indicate that, as far as the thermodynamic aspects of solvation of alkali halides are concerned, amorphous solid water and methanol surfaces behave similarly as surfaces of the corresponding liquids.
authors.affiliation: Technische Universität Clausthal, Institut für Physik und Physikalische Technologien, Leibnizstr. 4, D-38678 Clausthal-Zellerfeld, Germany.
authors.forename: Oliver
authors.initials: O
authors.lastname: Höfft
authors.forename: Andriy
authors.initials: A
authors.lastname: Borodin
authors.forename: Uwe
authors.initials: U
authors.lastname: Kahnert
authors.forename: Volker
authors.initials: V
authors.lastname: Kempter
authors.forename: Liem X
authors.initials: LX
authors.lastname: Dang
authors.forename: Pavel
authors.initials: P
authors.lastname: Jungwirth
mesh_terms: D007477:Ions; D012492:Salts / Q000737:chemistry*; D013499:Surface Properties
chemical_list: D007477:Ions; D012492:Salts