1. State
Key Laboratory of Precision Spectroscopy, East China Normal University, 3663 North Zhongshan Road, Shanghai 200062, China
2. Department
of Chemical Physics, University of Science and Technology of China, Hefei 230026, China
3. Department
of Physics, International Center of Quantum and Molecular Structures,
Shanghai Key Laboratory of High Temperature Superconductors, Shanghai University, Shanghai 200444, China