1. School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, United States
2. Chemistry and Chemical Biology Department, Cornell University, Ithaca, New York 14853, United States
3. Department of Chemistry, Institute for Molecular Engineering, and James Franck Institute, University of Chicago, Chicago, Illinois 60637, United States
4. Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, New York 14853, United States
5. Physics Department, Cornell University, Ithaca, New York 14853, United States
6. Kavli Institute at Cornell for Nanoscale Science, Ithaca, New York 14853, United States
7. Cornell High Energy Synchrotron Source, Cornell University, Ithaca, New York 14853, United States