[1] Cornell Univ, Atom & Solid State Phys Lab, Ithaca, NY 14853 USA
[2] SLAC Natl Accelerator Lab, Menlo Pk, CA 94025 USA
[3] DESY, Ctr Free Electron Laser Sci, Max Planck Adv Study Grp, D-22607 Hamburg, Germany
[4] Uppsala Univ, Dept Cell & Mol Biol, Lab Mol Biophys, SE-75124 Uppsala, Sweden
[5] Univ Calif Berkeley, Lawrence Berkeley Lab, Berkeley, CA 94720 USA
[6] Max Planck Inst Med Res, D-69120 Heidelberg, Germany
[7] Lawrence Livermore Natl Lab, Livermore, CA 94550 USA
[8] Univ Hamburg, D-22761 Hamburg, Germany