Berlin 2008 – scientific programme
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 19: SYMPOSIUM Driven Soft Matter IV
CPP 19.3: Talk
Wednesday, February 27, 2008, 14:30–14:45, C 130
Super-heterodyne light scattering as versatile tool to characterize multiphase flow — •Thomas Palberg1, Tetjana Köller1, and Gerhard Nägele2 — 1Institut f. Physik, Johannes Gutenberg Universität, Mainz — 2Institut für Festkörperforschung, Forschungszentrum Jülich GmbH., Jülich
Condensed matter put to extreme mechanical impact may react by crack formation, creep flow or even (partial) melting behaviour. Soft matter model systems may help in elucidating such phenomena due to both their softness, implying significant mechanical response even for small loads and their enlarged length and time scales, facilitating convenient optical access. Colloidal crystals in particular may display shear induced straining, local or global shear melting or shear induced crystallization, if subjected to shearing fields. Structural evolution may be monitored in detail using either video microscopy or time resolved static light scattering. We here show that incoherent scattering contributions (dominant at low scattering angles or selectively detected in VH geometry) can be exploited to provide the complementary information on the complex flow behaviour, without interference with the structural distribution. Super heterodyning in addition renders the data of interest free of homodyne contributions and low frequency noise. The combination of coherent and incoherent scattering experiments therefore may help in clarifying the coupling between structure and motion under shear. We exemplify our method studying an aqueous charged sphere suspension driven under the influence of different fields.