1. Institute of Atomic and Molecular Sciences, Academia Sinica, P.O. Box 23-166, Taipei 10716, Taiwan, R. O. C.
2. School
of Physics and Engineering, QuFu Normal University, QuFu, Shangdong 273165, P. R. C.
3. Department
of Chemistry, University of British Columbia, Vancouver, BC, Canada V6T 1Z1