Affiliation: | ZENG Wen-Sheng ****, YANG Xiao-Ming LI Zeng-Fa ZHANG Guang-Yin SONG De-Ying *and YAN Shao-Lin *Department of Physics, Nankai University, Tianjin 300071, P RC. **Department of Chemistry, Nankai University, Tianjin 300071, PRC. *** Department of Electric Science, Nankai University, Tianjin 300071, PRC.**** Present address: Department of Physics, Zhongshan University, Guangzhou 510275, PRC |