Berlin 2008 – scientific programme
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O: Fachverband Oberflächenphysik
O 93: Surface Chemical Reactions
O 93.9: Talk
Friday, February 29, 2008, 12:15–12:30, MA 043
Investigating the binding sites of solvated electrons in polar layers adsorbed on Cu(111) — •Michael Meyer, Julia Stähler, Uwe Bovensiepen, and Martin Wolf — Freie Universität Berlin, Arnimallee 14, 14195 Berlin
Electron solvation is a well known phenomena in polar environments like NH3 and D2O, i.e., the localization and energetic stabilization of an excess electron due to the reorientation of the surrounding molecules. The properties and dynamics of solvated electrons constitute an active field of research. Here we present a surface science approach to determine the solvation site of excess electrons at the interface between polar molecular layers and a metallic substrate. We investigate the localization of excess electrons in amorphous D2O clusters and layers as well as amorphous ammonia layers, which are condensed on a Cu(111) substrate. Using two-photon photoemission spectroscopy(2PPE) we excite and probe excess electrons by UV and VIS laser pulses, respectively. For surface bound electrons adsorption of Xe leads to a change in binding energy due to a change of the dielectric environment which is directly measured by 2PPE. A transition from bulk bound solvated electrons to surface bound ones is found to occur at coverages of ≈ 3 molecular layers where the continuous ice layers break up into laterally separated ice clusters. Remarkably the excess electrons in NH3-layers are always bound on the surface for the investigated thickness range of 2 to 22 layers. Possible scenarios regarding injection and detection probabilities as well as site configurations will be discussed.