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Creators/Authors contains: "Schäfer, Tim"

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  1. ; ; ; ; ; ; (, Frontiers in Chemistry)
    This study presents velocity-resolved desorption experiments of recombinatively-desorbing oxygen from Ag (111). We combine molecular beam techniques, ion imaging, and temperature-programmed desorption to obtain translational energy distributions of desorbing O 2 . Molecular beams of NO 2 are used to prepare a p (4 × 4)-O adlayer on the silver crystal. The translational energy distributions of O 2 are shifted towards hyperthermal energies indicating desorption from an intermediate activated molecular chemisorption state. 
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  2. ; ; ; ; ; (, Physical Chemistry Chemical Physics)
    We combine velocity map imaging (VMI) with temperature-programmed desorption (TPD) experiments to record the angular-resolved velocity distributions of recombinatively-desorbing oxygen from Rh(111). We assign the velocity distributions to desorption from specific surface and sub-surface states by matching the recorded distributions to the desorption temperature. These results provide insight into the recombinative desorption mechanisms and the availability of oxygen for surface-catalyzed reactions. 
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  3. ; ; ; ; (, ChemCatChem)
    Abstract The epoxidation of olefins on Ag/O systems is a significant industrial‐scale process within heterogeneous catalysis. However, the details of the surface reaction remain controversial, and it has been highly challenging to reconcile the findings from cataltyic studies under reaction conditions with the highly detailed static studies under carefully controlled ultra‐high vacuum (UHV) conditions. In this study, we combine molecular beam surface scattering and ion imaging techniques to explore the partial oxidation of styrene. This experimental approach enhances the sensitivity to the extent that we can directly observe the partial oxidation product, styrene oxide, under UHV conditions. We note that partial oxidation exclusively occurs at high oxygen coverages, which we attribute to the reaction of styrene with electrophilic oxygen formed specifically at elevated coverages. 
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