1. Department of Chemistry and Chemical Biology, Cornell University, Baker Laboratory, 162 Sciences Drive, Ithaca, New York 14853, United States
2. Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, Massachusetts 02138, United States
3. Department of Physics, Stanford University, Stanford, California 94305, United States
4. Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States