1. Department of Chemistry, Stanford University, Stanford, California 94305, United States
2. Institute for Physical Chemistry, Department of Chemistry, Heinrich-Heine-Universität Düsseldorf, Düsseldorf D-40225, Germany
3. Department of Chemistry, Duke University, Durham, North Carolina 27708, United States
4. SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States