1. Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58108, USA
2. Department of Physics and Astronomy, University of Rochester, Rochester, NY 14627, USA
3. Center for Integrated Nanotechnologies, Materials Physics and Applications Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
4. University of Pittsburgh, Pittsburgh, PA 15260, USA
5. Theory Division, Laboratory for Laser Energetics, University of Rochester, Rochester, NY 14627, USA