1. Department
of Physics, East China University of Science and Technology, Shanghai 200237, China
2. Department
of Physics and Engineering Physics, University of Saskatchewan, Saskatoon, Saskatchewan, S7N 5E2, Canada
3. Nano
and Molecular Systems Research Unit, University of Oulu, P.O. Box 3000, FIN-90014 Oulu, Finland
4. Canadian Light Source, Saskatoon, Saskatchewan, S7N 2V3, Canada