1. Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, BC, Canada, V6T 1Z1, Center of Molecular Science, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080, P. R. China, Department of Physics, University of Texas at Austin, Austin, Texas 78712-0264, and Communications Research Laboratory, Kansai Advanced Research Center, 588-2 Iwaoka, Kobe 651-2942, Japan