Author Affiliations

Thomas J. Penfold,¹ Jakub Szlachetko,^2,12 Wojciech Gawelda,^3,12 Fabio G. Santomauro,⁵ Alexander Britz,^3,4 Tim B. van Driel,⁶ Leonardo Sala,² Simon Ebner,² Stephen H. Southworth,⁷ Gilles Doumy,⁷ Anne Marie March,⁷ Carl S. Lehmann,⁷ Tetsuo Katayama,⁸ Melanie Mucke,¹¹ Denis Iablonskyi,¹⁰ Yoshiaki Kumagai,¹⁰ Gregor Knopp,² Koji Motomura,¹⁰ Tadashi Togashi,⁸ Shigeki Owada,⁹ Makina Yabashi,⁹ Jochen Rittmann,⁵ Martin M. Nielsen,⁶ Marek Pajek,¹² Kiyoshi Ueda,^9,10 Majed Chergui,⁵ Rafael Abela,² and Christopher J. Milne²

¹Department of Chemistry, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK

²Paul Scherrer Institute, 5232 Villigen-PSI, Switzerland

³European XFEL, D-22761 Hamburg, Germany

⁴The Hamburg Centre for Ultrafast Imaging, Luruper Chaussee 149, 22761 Hamburg, Germany

⁵Laboratoire de spectroscopie ultrarapide, ISIC, FSB and Lausanne Centre for Ultrafast Science (LACUS), École Fédérale de Lausanne, CH-1015 Lausanne, Switzerland

⁶Department of Physics, Technical University Of Denmark, 2800 Kongens Lyngby, Denmark

⁷Argonne National Laboratory, 9700 S. Cass Ave., Argonne, Illinois 60439, USA

⁸Japan Synchrotron Radiation Research Institute (JASRI), Kouto 1-1-1, Sayo, Hyogo 679-5198, Japan

⁹RIKEN SPring-8 Center, Kouto 1-1-1, Sayo, Hyogo 679-5148, Japan

¹⁰Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577, Japan

¹¹Department of Physics and Astronomy, Uppsala University, 751 20 Uppsala, Sweden

¹²Institute of Physics, Jan Kochanowski University, Świȩtokrzyska 15, 25-406 Kielce, Poland