Dresden 2003 – wissenschaftliches Programm
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O: Oberflächenphysik
O 38: Struktur und Dynamik reiner Oberfl
ächen
O 38.7: Vortrag
Freitag, 28. März 2003, 12:45–13:00, FOE/ANOR
Dynamics of liquid surfaces studied by X-ray photon correlation spectroscopy — •Christian Gutt1, Tuana Ghaderi1, Virginie Chamard1, Metin Tolan1, Anders Madsen2, and Tilo Seydel3 — 1Experimentelle Physik I, Universitaet Dortmund — 2ESRF, Grenoble, Frankreich — 3ILL, Grenoble, Frankreich
The surfaces of liquids are decorated by thermally excited capillary waves, which are responsible for an intrinsic roughness of liquid surfaces. While the static fingerprints of capillary waves have been studied in detail with X-ray reflectivity in the past there is only little information about the dynamic properties of the liquid surface. Here we report measurements of the dynamics of propagating capillary waves on a liquid water surface by means of X-ray photon correlation spectroscopy (XPCS). The experiment has been performed under conditions of grazing incidence with an incoming X-ray beam below the critical angle of total external reflection. From the measurement of the diffuse scattered signal the dispersion relation of propagating waves have been derived and found to be in good agreement with theory. In the q region investigated the measured intensity-intensity autocorrelation functions of the water surface have been found to be first order correlation functions instead the expected second order correlation function. This points towards a heterodyne coherent mixing, which may occur either from a coherence interference effect between the specular and diffuse signal or from parasitic scattering from Fraunhofer fringes of the micrometer sized pinholes used in coherence experiments.