1. Institute for Basic Science, Changwon National University, Changwon, 641-773, Korea
2. Department of Physics, Changwon National University, Changwon, 641-773, Korea
3. Department of Chemistry, Changwon National University, Changwon, 641-773, Korea
4. Department of Physics, Pukyoung National University, Pusan, 608-737, Korea