1. Department of Chemistry, Brown University, Providence, Rhode Island 02912, United States
2. Department of Chemistry, Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QZ, United Kingdom
3. Department of Physics and Astronomy, University of Nebraska - Lincoln, Lincoln, Nebraska 68588, United States
4. Department of Physics, Kansas State University, Manhattan, Kansas 66506, United States
5. SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States
6. European XFEL, Schenefeld 22869, Germany
7. Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, United States