Interstellar ices are main molecular reservoirs of the interstellar medium and are assumed to be responsible for a large part of the observed molecular diversity. In particular, their surface act as a catalysts for a lot of surface chemical reactions, but is also constantly affected by processes of exchanges with the gas phase, and thermal or energetic processing. The ice surface is moreover strongly connected to the ice porosity by pore collapse and crack formation processes which are triggered during ice processing. Studying the surface properties and porosity of these ices and especially their porosity is therefore crucial to constrain the physical and chemical evolution of the ISM.<br/>In order to treat these questions, we developed a mixed theoretical and experimental approach using state-of-the-art techniques to constrain the ice microstructure during both its deposition and heating upon desorption. First, small-angle neutron scattering experiments have been conducted at the ISIS facility; this allow a study of the ices at two angle ranges probing both the ice crystallinity but also its microstructure in terms of porosity and surface area. Secondly, classical molecular dynamics simulations have been implemented to study both deposition and heating of a water ice both on silicate and crystalline substrate. The microstructure of the ice is then measured regarding various parameters like the average thickness or the specific surface area.<br/>Results from both methods are finally gathered to draw a reasonable scenario about ice microstructural evolution in the interstellar medium and to propose better constraints to astrochemical models, in particular, about the surface evolution and how it drives the molecular exchanges between solid and gas phase

Porosity and micro-structure of interstellar ices: Insights from neutron scattering experiments and molecular dynamics simulations

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.