1. Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
2. Shenyang National Laboratory for Materials Science, Institute of
Metal Research, Chinese Academy of Sciences, Shenyang 110016, P.R. China
3. College of Sciences, Liaoning Shihua University, Fushun 113001, P.R. China
4. Physics and Astronomy Department, Michigan State University, East Lansing, Michigan 48824, United States
5. Department of Applied Physical Sciences, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States