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Astrophysics Luncheon Seminar

Adsorption and Chemical Reactions on Interstellar Grains: From H to Complex Organic Molecules
Presented by Yves Ellinger
Université Pierre et Marie Curie (Host: Paul Goldsmith)

Monday, July 15, 2013
12:00 noon in 169-336

Abstract
Most of the complex organic molecules (COMs) observed in the interstellar medium (ISM) are produced by solid-gas reactions involving at least one adsorbed partner. The adsorption energy that will govern the mobility of the species on the surface of the grains and the possibility for the newly formed molecule to remain on the surface or to return to the gas phase is an important data for astrochemical modeling. Adsorption energies may be determined by temperature programmed desorption (TPD) experiments or, alternatively, from first principle theoretical calculations, both methods supporting one another.

The results presented in this talk have been obtained in a systematic survey of the adsorption of volatiles of increasing complexity at the surface of interstellar grains. Three model surfaces are considered, i.e., crystalline water ice, graphene and hydroxylated silica. For obvious reasons, most of the effort has been devoted to water ice since this substrate is considered a major player in the synthesis of oxygen-containing molecules. But, as the temperature increases, the ice gets vaporized, the less bonded molecules being first released in the gas phase, followed by H2O, revealing the bare grain underneath on which molecules may re-adsorb and be ready for a new kind of reactivity. Selected typical results will be discussed and compared to experiments (Temperature Programmed Desorption) when available.


SVCP Astrophysics


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