1. Department of Chemistry, Kenneth S. Pitzer Center for Theoretical Chemistry, University of California, Berkeley and Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
2. Chemical Sciences Division and Ultrafast X-ray Science Laboratory, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
3. Department of Chemistry, University of California, Davis, California 95616, USA
4. Department of Chemistry, University of California, Berkeley and Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA