1. Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
2. Advanced Photon Source, Argonne National Laboratory, Lemont, Illinois 60439, USA
3. Technological Institute of Superhard and Novel Carbon Materials, Tsentralnaya str. 7a, Troitsk, Moscow 142190, Russia
4. Center for Molecular Movies, Department of Physics, Technical University of Denmark, DK-2800 Lyngby, Denmark