Journal Article

Laboratory investigations of the interaction between benzene and bare silicate grain surfaces

J. D. Thrower, M. P. Collings, F. J. M. Rutten and M. R. S. McCoustra

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 394, issue 3, pages 1510-1518
Published in print April 2009 | ISSN: 0035-8711
Published online April 2009 | e-ISSN: 1365-2966 | DOI:
Laboratory investigations of the interaction between benzene and bare silicate grain surfaces

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Experimental results on the thermal desorption of benzene (C6H6) from amorphous silica (SiO2) are presented. The amorphous SiO2 substrate was imaged using atomic force microscopy, revealing a surface morphology reminiscent of that of interplanetary dust particles (IDPs). Temperature-programmed desorption (TPD) experiments were conducted for a wide range of C6H6 exposures, yielding information on both C6H6–SiO2 interactions and the C6H6–C6H6 interactions present in the bulk C6H6 ice. The low-coverage experiments reveal complicated desorption behaviour that results from both porosity and roughness in the SiO2 substrate, and repulsive interactions between C6H6 molecules. Kinetic parameters were obtained through a combination of direct analysis of the TPD traces and kinetic modelling, demonstrating the coverage dependence of both desorption energy and pre-exponential factor. Experiments were also performed whereby the pores were blocked by pre-exposure of the SiO2 to water vapour. C6H6 was observed to be adsorbed preferentially on the SiO2 film not covered by H2O at the temperature at which these experiments were performed. This observation means that intermolecular repulsion likely becomes important at smaller C6H6 exposures on grains with a H2O mantle. Kinetic modelling of C6H6 multilayer desorption yields kinetic parameters in good agreement with previous studies, with the SiO2 having little impact on the desorption beyond the first few layers.

Keywords: molecular data; molecular processes; methods: laboratory; ISM: molecules

Journal Article.  6988 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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