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Hints on the evolution of the molecular complexity in space from quantum mechanical simulations

par Caroline CHAMPENOIS - publié le

séminaire

vendredi 12 juin 2015 à 11:00, service 322 du campus Saint-Jérôme

Albert Rimola
Departament de Química, Universitat Autònoma de Barcelona, Catalonia, Spain

Abstract
The existence of molecules and dust particles in the interstellar and circumstellar media has attracted the interest of astrophysicists, astrochemists and astronomers due to its relevance for the chemical evolution steps occurring in the deep space, which are relevant to the origin of life. Spectroscopic and photometric observations show that diffuse matter consisting of gas and submicron sized grains mixed together is present in the interstellar medium. Such a matter is not distributed evenly but aggregates in clouds that settle in the disk of spiral galaxies. In clouds where the density is about 1-10 H atoms cm-3 (the so-called diffuse clouds) grains consist of dust of Mg/Fe-silicates and carbonaceous materials, whereas in clouds with densities of about 10,000 H2 molecules cm-3 (the so-called dense clouds) dust grains are covered in ices of volatile species, thereby forming a core/mantle-type structure. The present knowledge of this interstellar matter is mostly based on spectroscopic observational data, supported by the comparison with laboratory experiments and on results from numerical astrochemical models. The combination of these three approaches has provided important information such as the chemical composition of grains or their chemical activity. However, atomic-scale information such as the detailed structure of the grain particles or precise reaction mechanistic steps is still lacking, which is a serious limitation to fully understand the physico-chemical steps leading to the increase of the chemical complexity in space. This information gap can partly be filled in by using theoretical calculations based on quantum mechanical approaches. In this seminar several examples on how these theoretical calculations can contribute to astrochemical studies in both rationalizing astronomical observations and puzzling experimental results will be presented. In particular, results obtained from simulations devoted to the formation of H2 on bare silicate surfaces, to the formation of H2CO and CH3OH through hydrogenation of CO on water ice surfaces, and to the formation of complex organic molecules from thermal activation of H2O-dominated dirty ices will be shown.

Contact local : Patrice Theulé

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