1. Professor Emeritus, Kobe University, Kobe 657-8501, Japan
2. Graduate School of Science, University of Hyogo, Kamigori, Hyogo 678-1297, Japan
3. Department of Physics, Osaka Metropolitan University, Sakai, Osaka 599-8531, Japan
4. Department of Physics, Kyushu University, Fukuoka 812-8581, Japan
5. National Institute for Quantum Science and Technology (QST), SPring-8, Sayo, Hyogo 679-5148, Japan