Regensburg 2007 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 11: INTERNAL SYMPOSIUM Scattering Experiments II

CPP 11.7: Talk

Tuesday, March 27, 2007, 16:15–16:30, H37

Speckle echo-technique for diffusing-wave spectroscopy of soft solids — •Pavel Zakharov and Frank Scheffold — University of Fribourg, Fribourg, Switzerland

We present a detection scheme for diffusing-wave spectroscopy (DWS) based on a two-cell geometry that allows efficient multi-speckle averaging with a single-mode detection. This is achieved by placing a fast-rotating diffuser in the optical path between laser and sample. We show that the recorded (multispeckle) correlation echoes provide an ensemble averaged signal without lengthy time averaging. Furthermore, combined with traditional two-cell DWS, the full intensity autocorrelation function can be measured with a single experimental setup. The scheme provides access to a large range of correlation times thus opening an experimental window for the study of slowly relaxing and arrested systems, such as viscoelastic complex fluids, colloidal glasses, and gels. We also demonstrate how the technique can be used to monitor dynamic properties of samples that evolve in time