Hamburg 2009 – wissenschaftliches Programm

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MO: Fachverband Molekülphysik

MO 16: Stossprozesse, Energietransfer 1

MO 16.4: Fachvortrag

Mittwoch, 4. März 2009, 15:15–15:45, VMP 6 HS-G

Electron-Exchange Parameter Measurements for Molecular Open-Shell-Targets — •Ingo Holtkötter and G. Friedrich Hanne — Department of Physics, Münster, Germany

Low-energy electron exchange collisions with simple open-shell molecules such as O₂, NO or NO₂ play an important role in both atmospheric physics and plasma chemistry. Due to the paramagnetic properties of these molecules, electron exchange collisions are experimentally observable. In our experiment, exchange collisions are investigated directly by measuring the change of spin polarization after the scattering of polarized electrons from unpolarized molecules with energies between 8 and 20 eV and scattering angles up to 130 ^∘. Since previous experimental results and theoretical calculations with O₂ and NO as targets were not in satisfactory agreement, we revived these measurements to gain a deeper insight into spin-exchange effects with open shell-molecules. Additionally, we achieved the first inelastical exchange parameter measurements for O₂. For NO₂, we present the first experimental results for differential elastic electron exchange scattering at low energies.

With our recent measurements, we get a detailed view of the discrepancies between the experimental and older theoretical results. New calculations for electron exchange processes with O₂ as target show a very good agreement with our data. In other cases, however, there are still discrepancies between the experimental results and theoretical calculations. Up to now, there are no calculations available for the exchange parameter for collisions with NO₂.