1. Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, China
2. Joint Institute for Nuclear Research, Joliot-Curie 6, Dubna 141980, Russia
3. The Institute of Nuclear Physics, Ibragimov St. 1, Almaty 050032, Kazakhstan
4. School of Nuclear Science and Technology, University of Chinese Academy of Sciences, Beijing 100049, China
5. Electron Microscopy Centre of Lanzhou University, Lanzhou University, Lanzhou 730000, China