1. Department of Physics and Engineering Physics, Tulane University 1 , New Orleans, Louisiana 70118, USA
2. School of Chemistry, University of Nottingham 2 , University Park, Nottingham NG7 2RD, United Kingdom
3. Hylleraas Centre for Quantum Molecular Sciences, Department of Chemistry, University of Oslo 3 , P.O. Box 1033, N-0315 Oslo, Norway