1. Laboratoire de Chimie Quantique, Institut de Chimie , Université de Strasbourg , 1 Rue Blaise Pascal , F-67008 Strasbourg , France
2. National Research Council Canada, Measurement Science and Standards , 1200 Montreal Road M-12 , Ottawa, ON K1A 0R6 , Canada
3. Department of Chemistry , Purdue University , 560 Oval Drive , West Lafayette, IN , USA
4. Department of Chemistry and Chemical Engineering, Royal Military College of Canada , P.O. Box 17000, Stn. Forces , Kingston, ON K7K 7B4 , Canada
5. Bureau International des Poids et Mesures, Pavillon de Breteuil F-92312 , Sèvres Cedex , France
6. ZHAW Zürich University of Applied Sciences , ICBT Institute for Chemistry and Biotechnology , Einsiedlerstrasse 31 , CH 8820 Wädenswil , Switzerland
7. Guest scientist at: ETHZ Swiss Federal Institute of Technology, Laboratory for Physical Chemistry, ETH Hönggerberg , Wolfgang-Pauli-Strasse 10 , CH-8092 Zürich , Switzerland , e-mail: