1. Department of Chemistry, Physical Chemistry, University of Paderborn, Paderborn, Germany
2. Center for Optoelectronics and Photonics Paderborn, University of Paderborn, Paderborn, Germany
3. Department of Physics, Theoretical Physics, University of Paderborn, Paderborn, Germany
4. Centre de Recherche Paul Pascal (CRPP), CNRS, Université Bordeaux, Pessac, France