Author Affiliations

D. M. Fritz,^1,* B. Adams,² C. Blome,⁷ P. H. Bucksbaum,¹ A. Cavalieri,¹⁰ S. Engemann,¹¹ S. Fahy,⁶ P. H. Fuoss,³ K. J. Gaffney,¹² P. Hillyard,¹¹ J. Kaspar,¹¹ A. M. Lindenberg,¹² S. H. Lee,¹ B. McFarland,¹ D. Meyer,¹¹ E. Murray,⁶ M. Nicoul,⁸ R. Pahl,⁵ J. Rudati,² D. P. Siddons,⁴ K. Sokolowski-Tinten,⁸ J. K. Wahlstrand,⁹ J. B. Hastings,¹² and D. A. Reis¹

¹FOCUS Center, Department of Physics and Applied Physics Program, University of Mchigan, Ann Arbor, MI 48109, USA

²Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439, USA

³Materials Science Division, Argonne National Laboratory, Argonne, IL 60439, USA

⁴National Synchrotron Light Source, Brookhaven National Laboratory, Upton, NY 11973, USA

⁵Consortium for Advanced Radiation Sources, The University of Chicago, Chicago, IL 60637, USA

⁶Department of Physics and Tyndall National Institute, University College, Cork, Ireland

⁷Deutsches Elektronen-Synchrotron DESY,Norkestrauss 85, 22607 Hamburg, Germany

⁸Institut fur Laser- und Plasmaphysik, Universitat Essen, 45117 Essen, Germany

⁹JILA and University of Colorodo, Boulder, CO 80309, USA

¹⁰Max-Planck-Institut of Quantum Optics,Hans-Kopfermann-Str. 1 D-85748, Garching, Germany

¹¹Department of Chemistry, Stanford University, Palo Alto, CA 94305, USA

¹²Stanford Synchrotron Radiation Laboratory, Menlo Park, CA, 94025, USA

^*Corresponding author: dmfritz@umich.edu