1. Graduate Group in Applied Science and Technology, University of California, Berkeley, California 94720, USA
2. Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
3. Department of Chemistry, University of California at Davis, Davis, California 95616, USA
4. Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan
5. PULSE Institute for Ultrafast Energy Science, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA