Berlin 2005 – scientific programme

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UP: Umweltphysik

UP 16: Atmosph
ärische Spurengase und Aerosole: Laboruntersuchungen

UP 16.3: Fachvortrag

Wednesday, March 9, 2005, 15:45–16:00, TU TA201

Radius, density and refractive index measurements of a single levitated aerosol droplet using white light resonance spectroscopy — •Ulrich Krieger and Alessandro Zardini — Institut für Atmosphäre und Klima (IACETH), ETH Zürich, 8093 Zürich, Schweiz

Up to now most of the atmospheric studies using an electrodynamic balance (EDB) to study single levitated aerosol particles have relied on the mass to charge ratio as the principle measure to determine hygroscopic growth.

Sizing liquid, spherical particles in an EDB by analyzing the angular dependent light scattering (scattering phase function) is often used. Alternatively one can obtain an elastic scattering-intensity spectrum from a particle either by varying the wavelength of the incident light or by varying the size of the scattering particle that is illuminated by a fixed wavelength light. Although these techniques are well established they have not been used extensively for atmospheric studies because of their lack of versatility, needing either a particle evaporating under quasi-steady conditions or a particle not changing in size studied with a laser system tunable over a wide wavelength range. We propose an alternative method measuring the Mie resonance spectra using a white light source. In addition, we propose to use a modified version of the periodic drag force technique to determine the density of the levitated particle. We will explain the basic concept and show first results on hygroscopic growth of sulfuric acid particles.