[1] DESY, Ctr Free Electron Laser Sci, Notkestr 85, D-22607 Hamburg, Germany
[2] Univ Hamburg, Hamburg Ctr Ultrafast Imaging, Luruper Chaussee 149, D-22761 Hamburg, Germany
[3] Max Planck Inst Struct & Dynam Matter, D-22761 Hamburg, Germany
[4] Ctr Free Electron Laser Sci, D-22761 Hamburg, Germany
[5] Univ Palermo, Dipartimento Fis & Chim, Via Archirafi 36, I-90123 Palermo, Italy
[6] Univ Hamburg, Dept Chem, Martin Luther King Pl 6, D-20146 Hamburg, Germany
[7] Flatiron Inst, Ctr Computat Quantum Phys CCQ, 162 Fifth Ave, New York, NY 10010 USA
[8] Univ Hamburg, Dept Phys, Luruper Chaussee 149, D-22761 Hamburg, Germany