1. Department of Chemistry, University of California at Berkeley, Berkeley, California 94720-1460, United States
2. Hylleraas Centre for Quantum Molecular Sciences, Department of Chemistry, University of Oslo, P.O. Box 1033, Blindern, 0315 Oslo, Norway
3. Department of Chemistry, University of California, Davis, California 95616, United States
4. Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States