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arXiv · 2404.02217

Measuring Absolute Velocities from Non-Equilibrium Oscillations via Single-Detector 3D Dynamic Light Scattering

José López-Molina·Arturo Moncho-Jordá·María Tirado-Miranda
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Abstract

Single-detector 3D dynamic light scattering (3D-DLS) emerges as a reliable technique to determine the drift velocity of out-of-equilibrium colloidal particles. In particular, our investigation reveals the appearance of oscillations of a well-defined frequency in the autocorrelation function of the scattered intensity when particles are immersed in a medium exposed to thermally induced convection. These oscillations arise as a consequence of the directed motion of particles due to the convective motion of the fluid. The experimental results obtained for different colloidal systems are corroborated by a theoretical model and thoroughly validated with fluid dynamics and Brownian dynamics simulations. The excellent agreement between experimental, theoretical and simulation data allows us to provide a solid and comprehensive explanation of the observed physical phenomena. This study via advanced dynamic light scattering (DLS) technique offers insights into the field of non-equilibrium particle dynamics, applicable not only to colloidal suspension affected by steady-state diffusion-convection but also to other non-equilibrium situations, such as systems driven by external fields (gravitational, electric or magnetic fields, among others).

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José López-Molina, Arturo Moncho-Jordá, María Tirado-Miranda. 2024-10-07. Measuring Absolute Velocities from Non-Equilibrium Oscillations via Single-Detector 3D Dynamic Light Scattering. https://arxiv.org/abs/2404.02217

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