Regensburg 2016 – wissenschaftliches Programm

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BP: Fachverband Biologische Physik

BP 10: Colloids and Complex Fluids III (Joint Session CPP/DY/BP)

BP 10.4: Vortrag

Montag, 7. März 2016, 15:45–16:00, H42

An empirical correction for multiple scattering in integral laser Doppler velocimetry experiments — •Denis Botin¹, Ludmila Marotta Mapa^1,2, Christopher Wittenberg¹, Holger Schweinfurt¹, and Thomas Palberg¹ — ¹Institute of Physics, JGU, D-55099, Mainz, Germany — ²Federal Univesity of Itajuba, Brazil

Super-heterodyne laser Doppler velocimetry (SHLDV) provides an integral measurement of the velocity distribution in electro-kinetic experiments[1]. This allows simultaneous evaluation of the electro-phoretic and electro-osmotic mobilities of the particles and along the cell wall, respectively [2]. Here, we introduce an extension of the method to the regime of concentrated samples, where multiple scattering affects the signal [3]. Multiple scattering distorts the signal shape, creating an additional hump in the background and prohibiting any meaningful fit. We use an empirical correction scheme for the spectra, in which we fit the multiple scattering contribution and subtract it from the raw data. This leaves the velocity dependent singly scattered contribution unaffected. First applications to measurements of the concentration dependence of the electro-phoretic mobility of charged colloidal spheres are reported.

[1]T. Palberg et al. J. Phys. Chem. 96, 8180 - 8183 (1992)

[2]T.Palberg et al. J. Phys.: Condens. Matter 24, 464109 (2012).

[3]H.C. Van de Hulst., *Multiple Light Scattering: Tables, Formulas, and Applications*, Academic Press, New York., (1980).