1. Division of Synchrotron Radiation Research, Department of Physics, Lund University, Box
118, 221 00 Lund, Sweden
2. Deutsches Elektronen-Synchrotron (DESY), 22607 Hamburg, Germany
3. II. Physikalisches Institut, Universität zu Köln, 50937 Köln, Germany
4. Aarhus Institute of Advanced Studies, Aarhus University, Aarhus C, DK-8000 Denmark
5. Department of Physics and Astronomy - Center for Interstellar Catalysis, Aarhus University, Aarhus C, DK-8000 Denmark
6. MAX IV Laboratory, Lund University, Box 118, 221 00 Lund, Sweden