1. Department of Molecular Materials Science, Graduate School of Science, Osaka City University, Sumiyoshi-ku, Osaka 558-8585
2. National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL 32306, U.S.A.
3. Graduate School of Natural Science & Technology, Okayama University, 3-1-1 Tsushimanaka, Okayama 700-8530
4. National Hellenic Research Foundation, Theoretical and Physical Chemistry Institute, Athens 116/35, Greece