1. Department
of Physics and Astronomy, Uppsala University, Box 516, 751 20 Uppsala, Sweden
2. European Synchrotron Radiation Facility, 71 Avenue des Martyrs, CS 40220, 38043 Grenoble Cedex 9, France
3. Organic
Materials and Devices, Friedrich-Alexander-Universität Erlangen-Nürnberg, Martensstraße 7, 91058 Erlangen, Germany
4. Petersburg Nuclear Physics Institute, Orlova Roscha, Gatchina, St. Petersburg 188300, Russia