1. Institute
of Chemical Materials, China Academy of Engineering Physics (CAEP), P.O. Box
919-327, Mianyang, Sichuan 621900, China
2. Department
of Mathematics and Physics, Officers College of CAPF, Chengdu 610213, China
3. College of Material Science and Engineering, Southwest University of Science & Technology, Mianyang, Sichuan 621900, China
4. Department
of Physics, University of Science and Technology of China, Hefei 230026, China