1. Department of Chemistry and Biochemistry University of Colorado Boulder CO 80309 USA
2. Current address: Dept. of Chemistry Ben-Gurion University of the Negev Beer-Sheva 84105 Israel
3. Harvard-Smithsonian Center for Astrophysics and School of Engineering & Applied Sciences Harvard University Cambridge Massachusetts 02138 USA
4. Current address: Institut des Sciences Moléculaires d'Orsay, CNRS Univ. Paris-Sud, Université Paris-Saclay Orsay France
5. JILA, National Institute of Standards and Technology and Department of Physics University of Colorado Boulder CO 80309 USA
6. Department of Physics Harvard University Cambridge MA 02138 USA
7. Department of Chemistry Massachusetts Institute of Technology Cambridge Massachusetts 02139 USA
8. Current address: Department of Chemistry Harvard University Cambridge MA 02138 USA
9. Current address: Department of Physics University of California Santa Barbara CA 93106 USA
10. Quantum Theory Project Depts. of Chemistry and Physics Univ. of Florida Gainesville FL 32611 USA