1. Beijing National Laboratory for Molecular Sciences, State Key laboratory for structural Chemistry of Unstable and Stable Species College of Chemistry and Molecular EngineeringPeking University Beijing 100871 P. R. China
2. Center for the Physics of Materials and Department of PhysicsMcGill University Montreal Quebec H3A 2T8 Canada
3. State Key Laboratory of Applied Organic ChemistryKey Laboratory of Special Function Materials and Structure DesignCollege of Chemistry and Chemical EngineeringLanzhou University Lanzhou 730000 P. R. China
4. Nanoacademic Technologies Inc. Suite 802, 666 Rue Sherbrooke West Montreal QC H3A 1E7 Canada
5. Institute of Physics, Chinese Academy of Science Beijing 100190 P. R. China