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arXiv · 2108.00741

Two-dimensional Brownian motion of anisotropic dimers

Daniel B. Mayer·Erick Sarmiento-Gómez·Manuel A. Escobedo-Sánchez·Juan Pablo Segovia-Gutiérrez·Christina Kurzthaler·Stefan U. Egelhaaf·Thomas Franosch
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Abstract

We study the 2D motion of colloidal dimers by single-particle tracking and compare the experimental observations obtained by bright-field microscopy to theoretical predictions for anisotropic diffusion. The comparison is based on the mean-square displacements in the laboratory and particle frame as well as generalizations of the self-intermediate scattering functions, which provide insights into the rotational dynamics of the dimer. The diffusional anisotropy leads to a measurable translational-rotational coupling that becomes most prominent by aligning the coordinate system with the initial orientation of the particles. In particular, we find a splitting of the time-dependent diffusion coefficients parallel and perpendicular to the long axis of the dimer which decays over the orientational relaxation time. Deviations of the self-intermediate scattering functions from pure exponential relaxation are small but can be resolved experimentally. The theoretical predictions and experimental results agree quantitatively.

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Daniel B. Mayer, Erick Sarmiento-Gómez, Manuel A. Escobedo-Sánchez, Juan Pablo Segovia-Gutiérrez, Christina Kurzthaler, Stefan U. Egelhaaf, Thomas Franosch. 2021-08-02. Two-dimensional Brownian motion of anisotropic dimers. https://doi.org/10.1103/physreve.104.014605

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