1. Xiamen Institute of Rare Earth Materials Haixi Institute, Chinese Academy of Sciences 361021 Xiamen P. R. China
2. Shanghai Institute of Applied Physics Chinese Academy of Sciences Zhang Heng Road No. 239, Pu Dong New District, P. O. Box 918 201204 Shanghai P. R. China
3. Department of Radiochemistry Shanghai Institute of Applied Physics Chinese Academy of Sciences 201800 Shanghai P. R. China