Erlangen 2018 – wissenschaftliches Programm

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UP: Fachverband Umweltphysik

UP 9: Poster session

UP 9.9: Poster

Mittwoch, 7. März 2018, 16:15–18:15, Orangerie

Ice nucleation on mesospheric nanoparticles: the first three monolayers — Mario Nachbar², Denis Duft¹, •Thomas Dresch², and Thomas Leisner^{1, 2} — ¹Institute for Meteorology and Climate Research - AAF, Karlsruhe Institute of Technology, Germany — ²Institute of Environmental Physics, Ruprecht-Karls-University of Heidelberg, Germany

Heterogeneous ice formation on meteoric smoke nanoparticles in the upper atmosphere is critical for the formation of mesospheric ice clouds, also known as noctilucent clouds. A better understanding of the microscopic dynamics of the condensation mechanisms is important for modeling the growth of ice particles and cloud formations in the mesosphere. All heterogeneous nucleation starts with the adsorption of single molecules from the vapor phase followed by the formation of the first few monolayers, where the influence of the core particle is still felt by the adsorbed water molecules. We present experimental data for the nucleation of 0.5 to 3.5 monolayers of water ice on Fe3O4 nanoparticles with diameters of 4 to 6 nm at temperatures between 150 to 160 K. By laser irradiation of the nanoparticles in a linear quadrupole ion trap under well controlled super-saturation conditions we precisely control the particle temperature. For each particle temperature the particle growth and the equilibrium number of adsorbed water molecules is directly measured in a Time-of-Flight mass spectrometer. From the measurements we obtain H2O sublimation rates as a function of particle temperature and relative desorption free enthalpies as a function of surface coverage.