1. Department of Chemistry, Michigan State University, 578 S. Shaw Lane, East Lansing, Michigan 48824, United States
2. Department of Chemistry, University of Connecticut, 55 North Eagleville Road, Storrs, Connecticut 06268-1712, United States
3. Department of Physics, Politecnico di Milano, Piazza Leonardo da Vinci, 32, Milan, Lombardy 20133, Italy