1. Hahn-Meitner Institut, Glienicker Str. 100, D-14109 Berlin, Germany; Istituto per i Processi Chimico-Fisici-CNR, via La Farina 237, 98123 Messina, Italy; Yuasa Corporation, 4-5-1 Ohgi-cho, Odawara 250-0001, Japan; ISIS Facility, Rutherford Appleton Laboratory, Chilton, OXON, U.K.; and Institut für Festkörperforschung, Forschungszentrum Jülich GmbH, D-52425 Jülich, Germany