Dresden 2011 – wissenschaftliches Programm
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UP: Fachverband Umweltphysik
UP 1: Poster Session
UP 1.14: Poster
Dienstag, 15. März 2011, 18:30–20:30, P2
XANES Studies of Supersaturated Salt Solutions by Optical Levitation — •Yan Zhang1, Alexei Erko2, Bernhard Wassermann1, and Eckart Rühl1 — 1Freie Universität Berlin, Institut für Chemie und Biochemie, Berlin, Takustraße 3, 14195, Berlin — 2Helmholtz Zentrum für Materialien und Energie-Speicherring BESSY II
We present the refined XANES spectra of single droplets of aqueous zinc bromide (ZnBr2), calcium bromide (CaBr2), and sodium bromide (NaBr) solutions kept in a metastable state by means of optical levitation. The saturation level of the levitated solution droplets of 15-25 micron was controlled by adjusting the humidity by using a Naflon membrane. The droplets were injected into the reactor where they were captured by a focused cw laser beam (λ=532 nm). A hard X-ray beam (4 - 15 keV) from the KMC-2 beamline (BESSY-II) was focused onto the levitated particles. XANES spectra of the droplets were taken by recording the X-ray fluorescence signal at the K-edges of Zn (9.6 keV) and Br (13.4 keV), respectively. The near-edge spectra of thin liquid films of the corresponding dilute salt solutions and pellets of solid crystals were also measured for a comparison. Characteristic spectral shifts and changes in intensity were observed in the XANES spectra as a function of the solute concentration. This is interpreted in terms of cluster formation occurring in supersaturated salt solutions. These results are compared to model calculations, experimental reference spectra of thin films of dilute solutions, as well as the solid samples.