Bremen 2017 – scientific programme

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UP: Fachverband Umweltphysik

UP 14: Atmosphäre - Aerosole/Wolken

UP 14.3: Talk

Thursday, March 16, 2017, 15:15–15:30, GW2 B3009

Characterization of optically-trapped submicron aerosol particles by ultraviolet broadband light scattering — •Kivanc Esat, Gregory David, Irina Ritsch, and Ruth Signorell — Laboratory of Physical Chemistry, ETH Zurich, Switzerland

Aerosol particles in the size range from a few 100 nanometers to a few microns have a large impact on our atmosphere. Their shape, size, refractive index, and composition are the key properties governing their interaction with light and determining the processes they experience in the atmosphere such as hygroscopic growth, nucleation and aging. Broadband light scattering (BLS) experiments on single isolated particles are useful to study such processes in the laboratory because they simultaneously measure the particle size and the wavelength-dependent refractive index. Our new BLS setup provides data in the UV and visible spectral ranges (320 - 700 nm). Inclusion of the UV spectral range is crucial for the sizing of submicron particles and allows for the retrieval of refractive indices in a range where such data are rare but urgently needed. In this presentation, we report the combination of a new BLS experiment with counter-propagating optical tweezers facilitating contactless characterization of particles as small as 300 nm. The presentation will highlight the broad applicability of the UV BLS experiment by means of four examples: 1) The sizing of calibrated submicron polystyrene latex sphere (PSL). 2) The evaporation of binary glycerol water droplets. 3) The hydration/dehydration cycling of aqueous potassium carbonate droplets. 4) Photochemical reactions of oleic acid droplets.