1. School of Chemical Sciences University of Chinese Academy of Sciences 19 Yuquan Road, Shijingshan District Beijing 100049 P. R. China
2. Beijing National Laboratory for Molecular Sciences College of Chemistry Peking University 5 Yiheyuan Road, Haidian District Beijing 100871 P. R. China
3. Beijing National Laboratory for Condensed Matter Physics, Institute of Physics Chinese Academy of Sciences 8 South 3rd Street Zhongguancun, Haidian District Beijing 100190 P. R. China
4. School of Physical Sciences University of Chinese Academy of Sciences 19 Yuquan Road, Shijingshan District Beijing 100049 P. R. China
5. Beijing Synchrotron Radiation Facility, Institute of High Energy Physics Chinese Academy of Sciences 19 Yuquan Road, Shijingshan District Beijing 100049 P. R. China