Dresden 2026 – wissenschaftliches Programm

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DY: Fachverband Dynamik und Statistische Physik

DY 61: Brownian Motion and Anomalous Transport

DY 61.3: Vortrag

Freitag, 13. März 2026, 10:00–10:15, ZEU/0118

Intensity countoscope: Quantifying dynamics from intensity correlations in real space — •Sophie Hermann and Sophie Marbach — PHENIX, Sorbonne Université/CNRS, Paris, France

Quantifying the dynamics of particle suspensions is of widespread interest in soft matter, including crystalline aggregates and bacterial colonisation. Here, we develop a new technique to learn about these dynamics directly from microscopy images. The intensity countoscope is based on the analysis of intensity correlations in virtual observation boxes of images. Through colloidal experiments, simulations, and theory, we demonstrate how this method determines equilibrium motion properties, such as self-diffusion coefficients and particle drift. By varying the size of the observation boxes, we can probe dynamics across length scales, disentangling contributions of the particle shape and the point spread function (PSF) from those of the particle motion. The intensity countoscope complements the broad range of existing techniques on interpreting images, such as particle tracking, sitting right in between dynamical differential microscopy (DDM), and particle number fluctuations (Countoscope). One strength is its applicability to situations where particle tracking is difficult, e.g. at high densities, with fast dynamics or with poor image resolution. Additionally, the entire analysis is performed in real space, which makes the technique computationally cheap as it does not require Fourier transformations. This also enables to find more intuitively physical meaning behind the obtained signals. This simplicity opens up broad perspectives on the study of collective phenomena and of interparticle interactions.

Keywords: Intensity correlations; Colloids; Microscopy analysis; Brownian diffusion; Diffusion coefficients