Dresden 2003 – wissenschaftliches Programm
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O: Oberflächenphysik
O 38: Struktur und Dynamik reiner Oberfl
ächen
O 38.1: Vortrag
Freitag, 28. März 2003, 11:15–11:30, FOE/ANOR
X-ay photon correlation spectroscopy of liquid surfaces — •Christian Gutt1, Tuana Ghaderi1, Virginie Chamard1, Metin Tolan1, Michael Sprung1, Anders Madsen2, and Tilo Seydel3 — 1Experimentelle Physik I, Universitaet Dortmund — 2ESRF, Grenoble, France — 3ILL, Grenoble, France
With the advent of 3rd generation synchrotron sources scattering with partially coherent X-rays has become possible. A partially coherent beam is produced by selecting the coherent part from an otherwise incoherent beam using micrometer-sized pinholes. In Surface X-Ray Photon Correlation Spectroscopy (XPCS) the time variation of a speckle pattern from the surface is used to extract information about the dynamics of the system. We report measurements of propagating capillary waves on a liquid water surface at T=5C with XPCS. The experiment has been performed under conditions of grazing incidence with an incoming X-ray beam below the critical angle oftotal external reflection. From the measurement of the diffuse scattered signal the dispersion relation of propagating capillary 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 liquid water surface have been found to be first-order correlation functions g1(τ) instead the expected second-order correlation functions g2(τ). This may be either due to a hetereodyne mixing with the fraunhofer fringes of the direct beam or due to coherent interference between the diffuse scattered beam and the total reflected beam on the surface at small q-values.