1. Helmholtz-Institut Jena, Fröbelstieg 3, 07743 Jena, Germany
2. GSI Helmholtzzentrum für Schwerionenforschung, 64291 Darmstadt, Germany
3. Theoretisch-Physikalisches Institut, Friedrich-Schiller-Universität Jena, 07743 Jena, Germany
4. Key Laboratory of Atomic and Molecular Physics & Functional Materials of Gansu Province, College of Physics and Electronic Engineering, Northwest Normal University, Lanzhou 730070, China