Author Affiliations

D. M. Fritz,^1,*,# B. Adams,^2,* C. Blome,^7,* P.H. Bucksbaum,^1,* A. Cavalieri,^11,* S. Engemann,^12,* S. Fahy,⁶ P. H. Fuoss,^3,* K. J. Gaffney,^13,* P. Hillyard,^12,* M. Horn-von Hoegen,⁸ M. Kammler,⁹ J. Kaspar,^12,* A. M. Lindenberg,^13,* S. H. Lee,^1,* B. McFarland,^1,* D. Meyer,^12,* E. Murray,⁶ M. Nicoul,^8,* R. Pahl,^5,* J. Rudati,^2,* D. P. Siddons,^4,* K. Sokolowski-Tinten,^8,* D. von der Linde,^8,* J. K. Wahlstrand,¹⁰ 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 für Experimentelle Physik, Universität Duisburg-Essen, 45117 Essen, Germany

⁹Institut für Halbleitertechnologie, Universität Hannover

¹⁰JILA and University of Colorodo, Boulder, CO 80309, USA

¹¹Max-Planck-Institut of Quantum Optics,Hans-Kopfermann-Str. 1D-85748, Garching, Germany

¹²Department of Chemistry, Stanford University, Palo Alto, CA 94305, USA

¹³Stanford Synchrotron Radiation Laboratory, Menlo Park, CA, 94025, USA

^*Also Member Subpicosecond Pulse Source Collaboration

^# dmfritz@umich.edu