1. Department of Physics and Materials Science Center, Philipps-University Marburg, Hans-Meerwein Str. 6, 35032 Marburg, Germany
2. Institute of Experimental Physics I and Center for Materials Research (ZfM), Justus-Liebig-University Giessen, Heinrich-Buff-Ring 16, 35392 Giessen, Germany
3. Institute of Theoretical Physics and Center for Materials Research (ZfM), Justus-Liebig-University Giessen, Heinrich-Buff-Ring, 35392 Giessen, Germany
4. Institute of Physical Chemistry, Justus Liebig University, Heinrich-Buff-Ring 17, 35392 Giessen, Germany
5. Center for Materials Research (ZfM), Justus-Liebig-University Giessen, Heinrich-Buff-Ring 16, 35392 Giessen, Germany
6. Institute of Organic Chemistry, Justus Liebig University, Heinrich-Buff-Ring 17, 35392 Giessen, Germany