Berlin 2001 – wissenschaftliches Programm
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AMPD: EPS AMPD
AMPD 5: Sitzung 5
AMPD 5.1: Vortrag
Mittwoch, 4. April 2001, 09:00–09:35, H105
WHEN AN ELECTRON MEETS A MOLECULAR ION: DISSOCIATIVE RECOMBINATION OF ATMOSPHERICALLY RELEVANT IONS — •Wim J. van der Zande — FOM Institute for Atomic and Molecular Physics, Kruislaan 407, 1098 SJ Amsterdam, The Netherlands
Molecular atmospheric physics aims at understanding the properties and composition of our atmosphere. This aim requires knowledge of the underlying microscopic physico–chemical processes. The same microscopic properties form the basis of many of the diagnostic tools, which are needed to determine the composition of our atmosphere in the absence of sufficiently accurate models or to corroborate these models. Light–driven reactions are obviously relevant, both by solar light and by thermal light from the earth. It is clear that laboratory data are needed to arrive at a quantitative description. Sometimes, our atmosphere can be considered as a giant laboratory, thanks to the presence of an impressive array of man-made detectors mounted in satellites, rockets, aeroplanes or in giant ground-based telescopes. I will present data from a laboratory experiment in a study of electron–molecular ion collisions using the heavy ion storage ring technique. These data are needed to quantify the efficiency of this mutual neutralisation process, which dominates the electron sink in the thermosphere. Both the underlying physical mechanisms as the implications for the study of the glows in our atmosphere will be discussed. Atomic products can be formed in different final states, some of which give rise to emission of radiation. The relative efficiency of the atomic states is determined and confronted with in situ data obtained in a rocket experiment. In the case of triatomic di–hydrides the complete three body fragmentation channel has been found to be the dominating channel. This at first sight surprising result will be explained and experiments for the case of water ions discussed.
[1] The ionospheric oxygen green airglow: electron temperature dependence and aeronomical implications, R. Peverall, S. Rosén, M. Larsson, J.R. Peterson, R. Bobbenkamp, S.L. Guberman, H. Danared, M. af Ugglas, A. Al-Khalili, A.N. Maurellis, W.J. van der Zande, Geophys. Res. Lett., 27, 481 (2000).
[2] Dissociative Recombination and Excitation of O2+: Cross Sections and Product Yields, Rob Peverall, Stefan Rosén, James R. Peterson, Mats Larsson, Ahmed Al-Khalili, Ljiljana Vikor, Jacek Semaniak, Arnaud Le Padellec and Wim J. van der Zande, J. Chem. Phys., In print, March 2001.
[3] Dynamics of three-body break-up in dissociative recombination: H2O+, S. Datz, R. Thomas, S. Rosén, A. Derkatch, F. Hellberg, M. Larsson, and W.J. van der Zande, Phys. Rev. Lett., 85, 5555 (2000).