1. Department of Chemistry, National Tsing Hua University, Hsinchu, Taiwan, R.O.C., Institute of Physics, Academia Sinica, Nankang, Taipei, Taiwan, R.O.C., Department of Chemistry, National Central University, Chungli, Taiwan, R.O.C., and Institute of Chemistry, Academia Sinica, Nankang, Taipei, Taiwan, R.O.C.