1. Graduate School of Engineering, Chiba University, 1-33 Yayoi-cho Inage-ku, Chiba 263-8522, Japan
2. Japan Atomic Energy Agency, Muramatsu 4-33, Tokai, Ibaraki 319-1194, Japan
3. High Field NMR Group, National Institute for Materials Science (NIMS), 3-13 Sakura, Tsukuba, Ibaraki 305-0003, Japan