1. Engineering Physics Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-8120, United States
2. Theiss Research, La Jolla, California 92037, United States
3. Department of Theoretical Chemistry, Technische Universität Dresden, 01062 Dresden, Germany
4. Department of Chemistry and the Texas Center for Superconductivity, University of Houston, Houston, Texas 77204-5003, United States