1. Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
2. Department of Physics and Photon Science, Gwangju Institute of Science and Technology (GIST), Gwangju 500-712, South Korea
3. Joint Center for Artificial Photosynthesis, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
4. Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States