Regensburg 2022 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 12: Poster 1

CPP 12.17: Poster

Monday, September 5, 2022, 18:00–20:00, P1

A scaled-down double-pass optical beam deflection setup for the measurement of diffusion and thermodiffusion in liquid mixtures — Mareike Hager, •Roman Reh, and Werner Köhler — Physikalisches Institut, Universität Bayreuth, Germany

We report about a compact double-pass optical beam deflection (OBD) setup for measurments on diffusion and thermodiffusion in liquid mixtures. A laserbeam transmitted through the sample gets back-reflected behind the OBD-cell and, thus, traverses the sample volume a second time. Applying a vertical temperature gradient to the sample leads to thermodiffusion and the beam gets deflected by the resulting gradient in refractive index due to the gradients in temperature and concentration. A beamsplitter guides the beam towards a camera, where the time dependent laserposition is recorded. The signal then gives information about the diffusion processes. Since the laserbeam propagates on the same path between the beamsplitter and the cell before and after getting deflected in the sample and since the double-transmission geometry allows little distance between cell and camera, the whole setup could be built very compact. Measurements with different binary mixtures are in good agreement with measurements with a single-transmission-OBD. We present a matrix formalism to describe the optical transfer function of the instrument.