1. Center for Free-Electron Laser Science, DESY, Notkestrasse 85, 22607 Hamburg, Germany
2. Department of Chemistry, Universität Hamburg, Grindelallee 117, 20146 Hamburg, Germany
3. Department of Physics, Universität Hamburg, Jungiusstrasse 9, 20355 Hamburg, Germany
4. The Hamburg Centre for Ultrafast Imaging, Luruper Chausee 149, 22761 Hamburg, Germany