1. Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
2. Department of Physics and Astronomy, University of Bologna, Bologna 40127, Italy
3. Chemistry Division, Brookhaven National Laboratory, Upton, New York 11973-5000, United States
4. Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina 27695-7905, United States