Berlin 2012 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 15: Poster: New Instruments and Methods

CPP 15.10: Poster

Tuesday, March 27, 2012, 18:15–20:15, Poster A

Space-resolved dynamic light scattering probing inhomogeneous dynamics in soft matter — •Sebastian Golde, Markus Franke, and Hans Joachim Schöpe — JoGu Universität Mainz, Institut für Physik, Staudinger Weg 7, 55099 Mainz, Germany

Dynamic light scattering (DLS) is the most powerful tool determining the dynamics in soft matter in a huge time interval of eleven decades. Using standard techniques the ensemble averaged dynamics can be determined in ergodic media. In nonergodic samples the time-averaged and the ensemble-averaged one differ. Special techniques have been developed (Interleaved sampling [1], Echo technique [2], multispeckle (MS) analysis [3]), measuring the intensity autocorrelation function (ICF) of many different coherent areas (speckles) simultaneously, in order to obtain ensemble averaged data. We here present a comparison of a new designed MS-DLS experiment with the Echo technique. In order to measure many speckles simultaneously we map the sample onto a fast CCD as a detector, which allows us to monitore the intensity of more than 500 speckles simultaneously and to connect each speckle with its origin scattering volume. Comparing the results from different method we obtain identical ensemble averaged results for colloidal hard sphere glasses. With the MS method we can achieve three decades shorter delay times than with the Echo method. Furthermore the MS setup allows us to measure time-resolved as well as space-resolved ICFs to probe differences in spatially separated subensembles. [1]Pr.Coll.Pol.Sci.100,121(1996) [2]Re.Sci.Inst. 75,2419(2004) [3]JCP 104,1758(1996)