Author Affiliations

B. K. McFarland,¹ J. P. Farrell,^1,2 S. Miyabe,¹ F. Tarantelli,³ A. Aguilar,⁴ N. Berrah,⁵ C. Bostedt,⁶ J. Bozek,⁶ P. H. Bucksbaum,^1,2 J. C. Castagna,⁶ R. Coffee,⁶ J. Cryan,^1,2 L. Fang,⁵ R. Feifel,⁷ K. Gaffney,¹ J. Glownia,^1,2 T. Martinez,^1,8 M. Mucke,⁷ B. Murphy,⁵ A. Natan,¹ T. Osipov,⁵ V . Petrovic,^1,2 S. Schorb,⁶ Th. Schultz,⁹ L. Spector,^1,2 M. Swiggers,⁶ I. Tenney,^1,2 S. Wang,^1,2 W. White,⁶ J. White,^1,2 and M. Gühr^1,*

¹PULSE, SLAC National Accelerator Laboratory, Menlo Park, CA 94025, USA

²Departments of Physics and Applied Physics, Stanford University, Stanford, CA 94305, USA

³Dipartimento di Chimica, Universita di Perugia, and ISTM-CNR, 06123 Perugia, Italy

⁴Advanced Light Source, Lawrence Berkeley National Lab, Berkeley, CA 94720, USA

⁵Physics Department, Western Michigan University, Kalamazoo, MI 49008, USA

⁶LCLS, SLAC National Accelerator Laboratory, Menlo Park, CA 94025, USA

⁷Department of Physics, Uppsala University, Uppsala, Sweden

⁸Department of Chemistry, Stanford University, Stanford, CA 94305, USA

⁹Max-Born-Institut, 12489 Berlin, Germany

^*Corresponding author: mguehr@slac.stanford.edu