1. Department of Mechanical Engineering, Stanford University 1 , Stanford, California 94305, USA
2. SLAC National Accelerator Laboratory 2 , Menlo Park, California 94025, USA
3. RIKEN SPring-8 Center 3 , 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148, Japan
4. Chemical and Materials Sciences Division, Pacific Northwest National Laboratory 4 , Richland, Washington 99354, USA