1. State Key Laboratory for Structural Chemistry of Unstable and Stable Species Institute of Chemistry Chinese Academy of Sciences Beijing 100190 P. R. China
2. Beijing National Laboratory for Molecular Sciences and CAS Research Education Centre of Excellence in Molecular Sciences Beijing 100190 P. R. China
3. Department of Mathematics and Physics North China Electric Power University Beijing 102206 China
4. University of Chinese Academy of Sciences Beijing 100049 P. R. China