1. Key Laboratory of Atomic and Molecular Physics and Functional Materials of Gansu Province, College of Physics and Electronic Engineering, Northwest Normal University 1 , Lanzhou 730070, China
2. School of Physics and Materials Science, Tianjin Normal University 2 , Tianjin 300387, China
3. School of Mechatronic Engineering, Handan University 3 , Handan 056006, China and School of Engineering and Mathematics and Physics, Hebei University of Engineering, Handan 056038, China
4. Helmholtz-Institut Jena 4 , Fröbelstieg 3, D-07743 Jena, Germany
5. GSI Helmholtzzentrum für Schwerionenforschung GmbH 5 , Planckstrasse 1, D-64291 Darmstadt, Germany