SMuK 2023 – wissenschaftliches Programm

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UP: Fachverband Umweltphysik

UP 1: Clouds in Planetary Atmospheres (joint session EP/UP)

UP 1.2: 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 clouds — Johanna Weidelt¹, •Thomas Dresch², Denis Duft², and Thomas Leisner^2,3 — ¹Ultrafast 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.