1. Neutron Science Laboratory, Institute of Materials Structure Science, High Energy Accelerator Research Organization, Tsukuba, Ibaraki 305-0801
2. Neutron Science Research Center, Japan Atomic Energy Research Institute, Tokai, Ibaraki 319-1195
3. ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot, Oxon, OX11 0QX, U.K.