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The modification of the Cu͑110͒ Shockley-type surface state by an adsorbed pentacene layer was determined using high-resolution angle-resolved photoelectron spectroscopy. It was found that the surface state is shifted by 80-120 meV to higher binding energies, depending on the pentacene coverage. In addition, an increase in the surface-state population is measured for the sample adsorbed with one monolayer of pentacene. The modification of the surface state by the adsorption of pentacene is put into relation to a complex interplay of different phenomena such as the hybridization and mixing of electronic states, the polarization of the adsorbate in the surface dipole, and the Pauli repulsion. Thus, this observation of a molecular adlayer shifting a surface state away from the Fermi energy sheds more light on the adsorbate-adsorbent interactions.

The gas phase hydrogenation of acrolein over silver has been studied in a broad pressure range from ~2 mbar to 20 bar and with various silver materials (single crystals, sputtered silver, silica supported Ag nanoparticles) in an attempt to examine the question of "pressure and materials gap" in catalysis. High pressures as well as nanoparticles favour the formation of allyl alcohol (selectivities up to 42 %), whereas with the opposite conditions propionaldehyde is by far the main product. A critical minimum reaction pressure was identified: below ca. 100 mbar no allyl alcohol was formed. In situ-XAS measurements have been performed at 7.5 mbar in order to gain insight into the interaction of acrolein with silver samples. Despite the fact that beam-induced processes have been observed, it is concluded that at low pressures, acrolein orientates parallel to the surface on Ag (111) and is present at the surface in the form of hydrogenated propionaldehyde-like species. The influence of catalyst structure and pressure on the adsorption geometry of acrolein as well as the possible rate-determining step in acrolein hydrogenation are discussed.