1. Department of Physics, Technical University of Denmark, Fysikvej 307, DK-2800 Kongens Lyngby, Denmark
2. The Hamburg Centre for Ultrafast Imaging, 22761 Hamburg, Germany
3. European XFEL GmbH, Holzkoppel 4, 22869 Schenefeld, Germany
4. SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
5. Physical Sciences Division, Pacific Northwest National Laboratory, Richland, Washington 99352, USA
6. Department of Chemistry, Technical University of Denmark, Kemitorvet 207, DK-2800 Kongens Lyngby, Denmark
7. Department of Chemistry, Faculty of Sciences, Universidad Autónoma de Madrid, Ciudad Universitaria Cantoblanco, 28049 Madrid, Spain
8. IMDEA-Nanociencia, Calle Faraday 9, 28049 Madrid, Spain
9. Chemical Physics, Lund University, P.O. Box 118, S-22100 Lund, Sweden
10. Wigner Research Centre for Physics, P.O. Box 49, H-1525 Budapest, Hungary
11. Department of Experimental Physics, Universität Hamburg, Jungiusstraße 9, 20355 Hamburg, Germany
12. Laboratoire de Spectroscopie Ultrarapide, ISIC-FSB Ecole Polytechnique Fédérale de Lausanne, Switzerland;
13. Deutsches Elektronen-Synchrotron DESY, Notkestraße 85, 22607 Hamburg, Germany