1. Physical Biology Center for Ultrafast Science and Technology, Arthur Amos Noyes Laboratory of Chemical Physics, California Institute of Technology, Pasadena, California 91125, USA
2. Deutsches Elektronen Synchrotron (DESY), Notkestraße 85, 22607 Hamburg, Germany
3. SwissFEL, Paul Scherrer Institut, 5232 Villigen PSI, Switzerland