1. Physics Department, Western Michigan University, Kalamazoo, Michigan 49008, USA
2. LCLS, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
3. Physics Department, University of Connecticut, Storrs, Connecticut 06269, USA
4. Chemical Sciences and Engineering Division, Argonne National Laboratory, 9700 South Cass Ave., Lemont, Illinois 60439, USA
5. Center for Free-Electron Laser Science, DESY, Notkestrasse 85, 22607 Hamburg, Germany
6. J. R. Macdonald Laboratory, Kansas State University, Manhattan, Kansas 66506, USA
7. Synchrotron SOLEIL, L’Orme des Merisiers, Saint-Aubin, BP 48, F-91192 Gif-sur-Yvette Cedex, France