1. Department of Physics and Information Technology, Shaanxi Key Laboratory for Phytochemistry, Baoji University of Arts and Sciences, Baoji, Shaanxi 721016, P. R. China
2. School
of Physics and Optoelectronic Engineering, Xidian University, Xi’an, Shaanxi 710071, P. R. China
3. College
of Chemistry and Chemical Engineering, Baoji University of Arts and Sciences, Baoji, Shaanxi 721013, P. R. China
4. National
Laboratory of Superhard Materials, Jilin University, Changchun, Jilin 130012, P. R. China