Book/Report

FZJ-2018-03686

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Heiße Reaktionen in Kometenanalogmaterialien durch Vakuumultraviolett-Photonen

Sauer, M.FZJ* ; Roessler, K.FZJ*

1991
Forschungszentrum Jülich GmbH Zentralbibliothek Verlag Jülich

Please use a persistent id in citations: http://hdl.handle.net/2128/19072

Report No.: Juel-2562

Abstract: The effects of vacuum-ultraviolet (VUV) photon irradiation on solid components of comet simulation experiments KOSI were studied in view of the behaviour of the nucleus in the solar radiation field. Among the substances were typical minerals (olivine, montmorillonite, kaolinite) and organic solids (hydrocarbon polymers, polyoxymethylene, kerogen, C-N-compounds such as triazene, adenine and guanidine). The vacuum of the irradiation chamber amounted to 2 $\cdot$ 10$^{-7}$ mbar, when cooling the samples to 77 K. A VUV-lamp (Hamamatsu L1835) was used with an intensity of 1.24 $\cdot$ 10$^{20}$ eV $\cdot$ s$^{-1}$m$^{-2}$ (20 J $\cdot$ s$^{-1}$ $\cdot$ m$^{-2}$) in the wavelength region between 110 and 300 nm (11.3 and 4.3 eV) . The proper VUV wavelength region between 110 and 170 nm could be filtered out in order to study the effects of hot H, C and N atoms formed via photodissociation by the high energetic photons. The maximum irradiation time of 6 h gave rise to radiation doses of several 100 eV per C or Si-atom of the substrate. Volatile fragments or new products were detected by mass spectrometry. The solid residues were analyzed by FT-IR spectrometry in reflectance and gas chromatography after heating at 150°C. The minerals, kerogen and the cyclic N-compounds proved to be very resistant against photolysis. Polymethylene and -ethylene showed only local irradiation effects such as formation of double bonds and liberation of molecules containing up to six carbon atoms. Polyoxymethylene (CH$_{2}$O)$_{n}$ yielded classical fragmentations to CO, CO$_{2}$, H$_{2}$CO, CH$_{3}$OH, CH$_{3}$O-groups and esters. Guanidine ejected HCN. It was observed that some effects did not depend on overall dose but on energy density, thus, indicating the participation of hot atoms. Compared to the effects of cosmic rays, the photon component of the inner solar system seems to lead to more destruction of complex molecules than to a build-up of these species. The VUV irradiation facilities have also been modified for use in comet simulation experiments KOSI, in particular to irradiate a spot on the surface of the cometary analog. Among the solid organic molecules to be studied by KOSI in future should bepolyoxymethylene, branched aliphatic and clefinic hydrocarbons and C-N-compounds such as guanidine.

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Contributing Institute(s):

1. Publikationen vor 2000 (PRE-2000)

Research Program(s):

1. 899 - ohne Topic (POF3-899) (POF3-899)

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Database coverage:

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