A. Scherz,1,* W. F. Schlotter,1,2 K. Chen,1,2 R. Rick,1,2 J. Stöhr,1 J. Lüning,1 I. McNulty,3,4 Ch. Günther,3 F. Radu,3 W. Eberhardt,3 O. Hellwig,3,5 and S. Eisebitt3 1SSRL, Stanford Synchrotron Radiation Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA 2Department of Applied Physics, 316 Via Pueblo Mall, Stanford University, Stanford, California 94035-4090, USA 3BESSY m.b.H.,...