1. Center for Free-Electron Laser Science, Notkestrasse 85, 22607 Hamburg, Germany
2. The Hamburg Centre for Ultrafast Imaging, Universität Hamburg, Luruper Chaussee 149, 22761 Hamburg, Germany
3. Department of Physics, Universität Hamburg, Luruper Chaussee 149, 22761 Hamburg, Germany
4. Molecular and Condensed Matter Physics, Department of Physics and Astronomy, Uppsala University, Box 516, 751 20 Uppsala, Sweden
5. Deutsches Elektronen-Synchrotron DESY, Notkestrasse 85, 22607 Hamburg, Germany