Einladung zum Promotionsvortrag von Herrn Philipp Auburger:
„Ab-initio investigation of dissociative electron attachment to halogenated hydrocarbons on the ice surface“
Nowadays atmospheric chemistry is of particular interest, since anthropogenic effects have a substantial influence on the global climate. E.g., the release of halogens andradicals, upon the issociation of industrially produced chlorofluorocarbons on catalytically active icy grains, is a precursor to environmentally hazardous ozone depleting reactions. Metal dopants enable the onset of these processes via photoinduced dissociative electron attachment (DEA) to the molecules.
The present study improves over previous investigations by following a systematic ab-initio approach and incorporating the influence of the ice substrate. GW calculations and underlying plane wave periodic supercell density functional theory (DFT) are employed. Subsequent BSE calculations give insight into direct photodissociation.
A comprehensive picture of the electronic structures relevant for DEA to the adsorbates is provided. The results are entirely consistent with the experimental observations, in particular those made by collaborateurs via cryogenic STM and 2PPE, and contribute significantly to their explanation. Analysing low-energy DEA to the prototypical phenyl halogenides yields a characteristic microscopic scenario. The excess electron is captured by a π* resonance and its internal conversion into a dissociative σ* state has to be activated. The reaction is favoured by a heavier halogen and adsorption. In particular the latter has a catalytic effect. It turns out that the agglomeration of surface dangling protons is the key aspect of both electron solvation and adsorption. Although strong electron traps are the preferential adsorption sites, DEA is induced by hot electrons. Direct photodissociation is excluded as a competitive process. (Vortrag auf Englisch)
Dem Vortrag schließt sich eine Diskussion von 15 Minuten an. Vortrag und Diskussion sind öffentlich. Diesen Verfahrensteilen folgt ein nicht öffentliches Rigorosum von 45 Minuten.