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SMuK 2023 – wissenschaftliches Programm

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EP: Fachverband Extraterrestrische Physik

EP 3: Clouds in Planetary Atmospheres (joint session EP/UP)

EP 3.2: Vortrag

Dienstag, 21. März 2023, 17:00–17:15, ZEU/0160

Preferential adsorption of para and ortho water molecules on charged nanoparticles in planetary ice cloudsJohanna Weidelt1, •Thomas Dresch2, Denis Duft2, and Thomas Leisner2,31Ultrafast Science Research Unit, University of Bielefeld, Germany — 2Institute of Meteorology and Climate Research, Karlsruhe Institute of Technology, Germany — 3Institute of Environmental Physics, University of Heidelberg, Germany

In the Earth mesopause, nanometer-size singly charged particles form by condensation of evaporated meteorite material. They exhibit an enhanced water adsorption cross section due to the strong charge-dipole-interaction. In this work, we study how the nuclear spin state of water molecules affects this enhancement and whether there are conditions that could lead to the formation of spin-polarized ice. Due to symmetry constraints on the total molecular wavefunction, ortho (proton spins parallel) and para (spins antiparallel) water occupy different rotational states, resulting in a different average dipole orientation in electric fields. Therefore, we expect ortho and para water to exhibit distinct adsorption enhancement factors onto charged nanoparticles. Based on Stark-shifts of individual rotational states of water, average dipole orientations of a molecular ensemble and the resulting collision cross section was calculated for various temperatures and particle sizes. We found that in the mesosphere of the Earth (T~150K) the adsorption enhancement of ortho- and para- water is approximately equal while at lower temperatures prevailing around ice giant planets and their moons, significant spin polarizations up to 15% occur.

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