1. Department of Physics, Tohoku University, Sendai 980-8578, Japan
2. Department of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
3. Department of Chemistry, North Carolina State University, Ralleigh, NC 27695-8204, U.S.A.
4. ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot, OX11 0QX, U.K.
5. LANSCE, Los Alamos National Laboratory, Los Alamos, NM 87545, U.S.A.
6. Quantum Beam Science Directorate, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195, Japan
7. WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan