Berlin 2005 – scientific programme

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DY: Dynamik und Statistische Physik

DY 43: Einstein Symposium Brownian Motion, Diffusion and Beyond (SYBM) – Contributed Talks I

DY 43.12: Talk

Tuesday, March 8, 2005, 17:15–17:30, TU H2032

Brownian motion of a single levitated mixed phase aerosol particle: Probing the dynamics of coupled Brownian motion employing dynamic light scattering — •Ulrich K. Krieger — Institute for Atmospheric and Climate Science (IACETH), ETH Zurich, 8093 Zurich, Switzerland

Within a liquid atmospheric aerosol particle a solid phase may coexist with the liquid over a wide range of ambient conditions. Aerosol particles often contain water insoluble components such as mineral dust or soot. Or, depending on composition, temperature, and relative humidity, a solid phase may form in an aqueous multicomponent salt particle, leaving a substantial fraction of the total particle mass in the liquid phase.

We apply dynamic light scattering spectroscopy (DLS) to probe the dynamics of single mixed phase particles levitated in a quasi-electrostatic trap under standard gas pressure. The Brownian motion of these particles is complicated because it is a coupled motion of the host droplet suspended in the gas phase and the movement of the inclusion via the viscous drag in the liquid phase. However, the analysis may allow obtaining information not only on the sizes of the host droplet and the inclusion but also on the viscosity of the liquid phase.

We will present experimental data and outline a route for interpreting the dynamic light scattering in the framework of coupled Brownian motion.