8th Liquid Matter Conference September 6-10, 2011 Wien, Austria ...

P8.10Thu 811:10-14:00Measurements of the dynamic susceptibility of colloidalsuspensions using coherent X-raysHeiko Conrad, 1 Louisa Dahbi, 1 Birgit Fischer, 1 Christian Gutt, 1 and GerhardGruebel 11 Hasylab/DESY, Notkestr. 85, 22607, Hamburg, GermanyA coherent X-ray beam scattered by a quasi-static disordered sample generates a specklepattern which reflects the exact spatial arrangement of the particles. By calculating the timeautocorrelation function the characteristic time scale of the dynamics can be extracted from thespeckle pattern. In this context colloidal particle are often used as tracer to detect the dynamicsin molecular glass former. We studied silica particles in glass forming liquids with a size ofabout 50-100 nm using X-ray photon correlation spectroscopy (XPCS) coupled with small-angleX-ray scattering (SAXS) to investigate the glass transition phenomena. We present our latestdata applying the four-point density correlator G 4 as a function of temperature and wave vectortransfers for which the theory of the usual glass formation models predicts notable differences inthe behavior of the corresponding dynamic four-point susceptibility function χ 4 [1, 2].[1] L. Cipelletti H. Bissig, V. Trappe, P. Ballesta, S. Mazoyer, J. Phys. Condens. Matter,15 257 (2003).[2] C. Toninelli, M. Wyart, L. Berthier, G. Biroli and J. P. Bouchaud, Phys. Rev. E 71, 41505(2005).10