1. School of Chemistry, University of Nottingham, University Park, Nottingham NG7 2RD, United Kingdom
2. Department of Physics and Engineering Physics, Tulane University, New Orleans, Louisiana 70118, USA
3. Institute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 1999/2, CZ-182 21 Prague, Czech Republic
4. Hylleraas Centre for Quantum Molecular Sciences, Department of Chemistry, University of Oslo, P.O. Box 1033 Blindern, N-0315 Oslo, Norway
5. Centre for Advanced Study at the Norwegian Academy of Science and Letters, Drammensveien 78, N-0271 Oslo, Norway