1. Institute of Physics, University of Freiburg, Hermann-Herder-Str. 3, 79104 Freiburg, Germany
2. Institut für Kernphysik, J. W. Goethe-Universität, Max-von-Laue-Strasse 1, 60438 Frankfurt am Main, Germany
3. Molecular Physics, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
4. European XFEL, Holzkoppel 4, 22869 Schenefeld, Germany
5. Elettra-Sincrotrone Trieste S.C.p.A., 34149 Basovizza, Trieste, Italy
6. Department of Physics, University of Gothenburg, Origovägen 6 B, 41296 Gothenburg, Sweden
7. Deutsches Elektronen-Synchrotron DESY, Notkestr. 85, 22607 Hamburg, Germany
8. The Hamburg Centre for Ultrafast Imaging CUI, Luruper Chaussee 149, 22761 Hamburg, Germany
9. Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, 8000 Aarhus, Denmark
10. IFN-CNR and Dipartimento di Fisica, Politecnico di Milano, Piazza L. da Vinci 32, 20133 Milano, Italy
11. Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Frascati, Via E. Fermi 40, 00044 Frascati, Roma