1. State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 11602, P. R. China, State Key Laboratory of Molecular Reaction Dynamics, Center of Molecular Science, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080, P.R. China, and Department of Physics, Anhui Normal University, Wuhu, Anhui Province 241000, P.R. China