1. Department of Physics National Cheng Kung University Tainan 701 Taiwan
2. Department of Physics Princeton University Princeton NJ 08544 USA
3. Department of Chemistry Princeton University Princeton NJ 08544 USA
4. Department of Physics and Astronomy University of Missouri Columbia MO 65211 USA
5. Department of Physics National Tsing Hua University Hsinchu 30013 Taiwan
6. The Advanced Light Source Lawrence Berkeley National Laboratory Berkeley CA 94720 USA
7. Department of Physics University of Connecticut Storrs CT 06269 USA
8. Institute of Physics Academia Sinica Taipei 11529 Taiwan
9. Physics Division National Center for Theoretical Sciences Hsinchu 30013 Taiwan
10. Condensed Matter Physics and Materials Science Brookhaven National Laboratory Upton NY 11973 USA
11. Department of Chemistry Louisiana State University Baton Rouge LA 70803 USA