Berlin 2014 – wissenschaftliches Programm
UP 10.2: Vortrag
Mittwoch, 19. März 2014, 14:30–14:45, MAG 100
Raman spectroscopy of levitated glassy aerosols — •Andreas Peckhaus, Alexei Kiselev, and Thomas Leisner — Karlsruher Institut für Technologie (KIT), Karlsruhe, Baden-Württemberg
Recent field measurements showed that ice clouds in the upper troposphere exhibit low ice particle number concentrations and high in-cloud relative humidities with respect to ice, which is explained by the suppression of crystallization by glassy aerosols. Aqueous sucrose solution droplets levitated in an electrodynamic balance (EDB) are used as a proxy for highly oxygenated organic compounds showing a glass transition or homogeneous freezing behavior depending on the temperature and relative humidity. We present trajectories of the phase diagram which clearly reveal the formation of a glassy amorphous state and ice nucleation. The deliquescence of a crystalline and an amorphous aerosol at different temperatures is reported. By means of angle-resolved Mie scattering pattern of levitated aerosol droplets the onset of the phase transition can be detected. In addition, the Raman spectroscopy is used to study phase transitions at characteristic points of the trajectory. Both methods used make it possible to experimentally derive a phase diagram of the binary mixture of sucrose and water and compare it with theoretical expectations.