1. Department of Applied Physics Waseda University Shinjuku Tokyo 169‐8555 Japan
2. Sincrotrone Trieste S.C.p.A. Area Science Park, Basovizza Trieste 34012 Italy
3. Department of Chemistry Tokyo Institute of Technology Meguro Tokyo 152‐8551 Japan
4. Hiroshima Synchrotron Radiation Center Hiroshima University Hiroshima 739‐0046 Japan
5. Department of Applied Physics The University of Tokyo Bunkyo Tokyo 113‐8656 Japan
6. Department of Physics Okayama University Okayama 700‐8530 Japan
7. Department of Physics Osaka University Toyonaka Osaka 560‐0043 Japan
8. Department of Quantum Matter Hiroshima University Hiroshima 739‐8530 Japan
9. Department of Physics Universitá di Roma “La Sapienza,” Rome 00185 Italy