1. Department of Chemical Engineering; Stanford University; Stanford California 94305 USA
2. Department of Physics; North Carolina State University; Raleigh NC 27695 USA
3. College of Chemistry, Peking University; Beijing 100871 China
4. Department of Materials Science and Engineering; Stanford University; Stanford California 94305 USA
5. Stanford Synchrotron Radiation Lightsource; SLAC National Accelerator Laboratory; Menlo Park California 94025 USA
6. Department of Physics and Astronomy; University of Rochester; Rochester NY 14627