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Title: Speckle-visibility spectroscopy: A tool to study time-varying dynamics
Authors: Bandyopadhyay, Ranjini
Gittings, A.S.
Suh, S.S.
Dixon, P.K.
Durian, D.J.
Issue Date: Sep-2005
Publisher: American Institute of Physics
Citation: Review of Scientific Instuments, 2005, Vol.76, p093110
Abstract: We describe a multispeckle dynamic light scattering technique capable of resolving the motion of scattering sites in cases that this motion changes systematically with time. The method is based on the visibility of the speckle pattern formed by the scattered light as detected by a single exposure of a digital camera. Whereas previous multispeckle methods rely on correlations between images, here the connection with scattering site dynamics is made more simply in terms of the variance of intensity among the pixels of the camera for the specified exposure duration. The essence is that the speckle pattern is more visible, i.e., the variance of detected intensity levels is greater, when the dynamics of the scattering site motion is slow compared to the exposure time of the camera. The theory for analyzing the moments of the spatial intensity distribution in terms of the electric-field autocorrelation is presented. It is tested for two well-understood samples, a colloidal suspension of Brownian particles and a coarsening foam, where the dynamics can be treated as stationary and hence can be benchmarked by traditional methods. However, our speckle-visibility method is particularly appropriate for samples in which the dynamics vary with time, either slowly or rapidly, limited only by the exposure time fidelity of the camera. Potential applications range from soft-glassy materials, to granular avalanches, to flowmetry of living tissue.
Description: Open Access.
ISSN: 0034-6748.
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Copyright: 2005 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics.
Appears in Collections:Research Papers (SCM)

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