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(15-42) Atmospheric chemical studies of optically levitated single micro-droplets. Mund, Christian1, Jordanov, Nicolai*,1, Zellner, Reinhard1, 1 University of Essen, Universitätsstr. 5, 45117 Essen, Germany ABSTRACT- Aerosols play an important role in the chemistry of the atmosphere. They provide surfaces for heterogeneous processes or act as a sink for trace species. Their optical properties have an impact on the radiative forcing of the atmosphere. Laboratory experiments on bulk samples do not necessarily reveal the behaviour of small particles due to their interaction with the walls of the vessel. Therefore, an experimental setup has been developed to study single micro-droplets at low temperatures. These particles are held contact-free by means of optical levitation within a focused laser beam. The composition of the droplets is derived from an analysis of the inelastically scattered light (Raman-scattering), whereas information of their size is determined by the elastically scattered light (Mie-scattering). Single atmospheric droplets (e.g. aqueous solutions of sulfuric acid, nitrates, and sulfates) have been trapped and studied for several hours. During these experiments the relative humidity and the temperature of the gas phase surrounding the particles have been varied leading to evaporation and condensation processes. Metastable states far from thermodynamic equilibrium could be observed, where the droplets showed strong supercooling and supersaturation. Key words: particle, levitation, microphysics |
