Science and Engineering at The University of Edinburgh

Soft Condensed Matter, Biological Physics Experiment & Statistical Physics Seminars

Wednesday 7 Dec 05 - 12:30pm

X-ray Photon Correlation Spectroscopy as a new tool to investigate the dynamics of soft condensed matter

Aymeric Robert

Complex relaxations in disordered systems have been studied successfully by scattering of both visible light and neutrons. Neutron based techniques can probe the dynamic properties of matter at high frequencies from f typically equal to 10^14 Hz down to about 10^7 Hz and achieve atomic resolution. Photon Correlation Spectroscopy (PCS) with visible light can cover the low frequency dynamics (f < 10^6 Hz) but probes only the long wavelength regions (Q < 4.10^-2 nm^-1) in materials not absorbing visible light. Coherent hard X-ray beams from third generation synchrotron sources open up the possibility for Correlation Spectroscopy experiment with X-ray (XPCS) capable of studying slow dynamics (10^6 Hz to 10^-3 Hz) on submicron lengthscales in dilute and concentrated (optically opaque) systems, and is not subject to multiple scattering [1,2]. This technique can be used in two different geometries namely in the Small Angle or in Reflectivity, depending if one is interested to probe bulk or surface dynamics respectively. We will review the status of this technique [1,2] by discussing its applications for the study of the complex dynamic behavior of soft condensed systems [1,2] and will focus especially on recent examples, among which the study of the hydrodynamics of charge-stabilized magnetic colloidal dispersions [2,3], but as well the investigation of aging of the alpha relaxation in a glassy ferrofluid [4].

[1] G. GrĂ¼bel et al, J. Alloys. Compd. 362, 3 (2004)
[2] A. Robert et al., J. Magn. Magn. Mat 289 , 47 (2005)
[3] A. Robert et al., J. Chem. Phys. 122 , 084701 (2005)
[4] Submitted

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