1. S. Chen, R. S. Ingram, M. J. Hostetler, J. J. Pietron, R. W. Murray, Department of Chemistry, Kenan Laboratories, University of North Carolina, Chapel Hill, NC 27599–3290, USA.
2. T. G. Schaaff, J. T. Khoury, M. M. Alvarez, R. L. Whetten, Schools of Chemistry and Physics, Georgia Institute of Technology, Atlanta, GA 30332–0430, USA.