1. Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
2. Department of Physics, University of Wisconsin Madison, Madison, Wisconsin 53706, USA
3. Department of Physics, University of California, Davis, California 95616, USA
4. Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
5. Ångström Solar Center, Uppsala University, Box 534, SE-751 21 Uppsala, Sweden
6. Department of Physics, University of California, Berkeley, California 94720, USA
7. Department of Chemistry, University of Wisconsin Madison, Madison, Wisconsin 53706, USA