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Experimental Spectroscopy Atmospheric
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Andrew Gibbons

Background

  • BA in chemistry, ULB (2009-2012)
  • MA in chemistry, ULB (2012-2014)
  • Internship: Evaluation et analyse de sensibilité d'un modèle chimique d'une atmosphère cométaire, BIRA-IASB (2013)
  • Master thesis: Etude par dynamique moléculaire de la discrimination de différents ligands par AdiC, un antiporteur arginine:agmatine impliqué dans la résistance acide chez E. coli
  • PhD student in Sciences, ULB, BELSPO grant (BIRA-IASB) (2014-present)

PhD project

A study of reactions occuring at cometary surfaces.
The Rosetta satellite launched by the European Space Agency has recently arrived at comet 67P/Churyumov-Gerasimenko (67P/C-G). As it gets nearer to the sun, the cometary surface becomes active, emitting gas and dust particles as a result of surface heating. The ROSINA instrument (Rosetta Orbiter Spectrometer for Ion and Neutral Analysis) aboard Rosetta measures the composition of the cometary atmosphere (also called coma) resulting from said emissions through the high-resolution mass spectrometer DFMS (Double Focusing Mass Spectrometer). Modeling of the coma isn't a straightforward problem due to the lack of data concerning the temperature dependence of the reaction rates used to describe the chemical phenomena occuring in it.
In order to make up for this lack of data, the desorption of some crucial chemical species (such as methanol) for the description of coma chemistry from cometary surfaces will be studied using a combined classical and quantum mechanical QM/MM approach. In this method, the bulk of the surface is described using classical mechanics, while the interface between the surface and the adsorbed chemical species is described quantum-mechanically. A computational strategy involving quantum dynamics based on the evolution of wave packets will be applied. SUch a strategy brings the advantage of being able to calculate the reaction rates of both chemical desorption and photodesorption (induced by an electromagnetic field). Particular care will go into the description of the composition and topology of the cometary surface, since its coarseness will greatly influence desorption phenomena occuring at its surface. This information will be derived from literature or from data sent back by the COSIMA instrument aboard Rosetta analysing dust grain composition.
The calculated desorption rates will be included in the ROSINA/DFMS flow chemistry model describing the expansion and chemical phenomena of the coma of comet 67P/C-G developed by Prof. Johan De Keyser of the Belgian Institute for Space Aeronomy (BIRA-IASB). Preliminary work is being done at BIRA-IASB on the calibration optimisation of the ROSINA/DFMS mass spectra in order to select the chemical species of interest based on the actual coma measurements made by Rosetta.

Publications

See here.

Contact

Laboratoire de Chimie Quantique et Photophysique (http://www.ulb.ac.be/cpm),
Université libre de Bruxelles, CP160/09
50 Av. F.D. Roosevelt, B-1050 Belgium
E-mail


Université Libre de Bruxelles – Faculté des Sciences