Greifswald 2024 – scientific programme

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UP: Fachverband Umweltphysik

UP 1: Atmospheric Trace Gases and Aerosols

UP 1.3: Talk

Monday, February 26, 2024, 11:45–12:00, ELP 6: HS 4

A novel method of measuring the viscosity and surface tension of supercooled levitated droplets — Mohit Singh¹, Stephanie Helen Jones¹, Alexei Kiselev¹, Denis Duft¹, and •Thomas Leisner^1,2 — ¹Institut of Meteorology and Climate Research, Karlsruhe Institute of Technology, Karlsruhe, Germany — ²Institut für Umweltphysik, Universität Heidelberg, Germany

Viscosity and surface tension of aerosol particles influence e.g. the rate of heterogeneous and photochemical reactions, the evaporation and growth processes leading to CCN formation, and the ability to act as ice nuclei. Both quantities can vary significantly during the atmospheric processing of aerosol particles. Following these changes requires a fast and reliable measurement technique, which can be applied to airborne particles under realistic atmospheric conditions where noneequilibrium conditions like supersaturation and superooling are widespread. We report a novel method to simultaneously measure the time-dependent viscosity and surface tension of charged droplets levitated in an environmental electrodynamic balance. In addition to the alternating electric field required for levitation, a secondary electric field of variable frequency is applied to induce shape oscillations in the levitated droplet. The shape oscillations are analysed by light scattering and the phase shift in the induced shape oscillations with respect to the driving field is used to determine droplet viscosity and surface tension.

Keywords: Aerosols; Light scattering; Levitated particles; Viscosity; Surface tension