1. Research Institute of Advanced Materials (RIAM), Hyperstructured Organic Materials Research Center (HOMRC), and School of Materials Science and Engineering, Seoul National University, San 56-1, Shillim-dong, Gwanak-gu, Seoul 151-742, Korea, and Radiation Science Center, High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801, Japan