1. Department of Physics, Dalian Maritime University, Dalian, China 116026
2. Department of Chemistry and Biochemistry, Florida International University, Miami, Florida 33199
3. Institute of Atomic and Molecular Sciences, Academia Sinica, P.O. Box 23-166, Taipei, Taiwan 10764 and Department of Applied Chemistry, National Chiao-Tung University, Hsin-chu, Taiwan