1. Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, United States
2. Max-Planck-Institut für Bioanorganische Chemie, Stiftstrasse 34-36, D-45470 Mülheim an der Ruhr, Germany
3. Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
4. Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States