1. Physikalisches
Institut, Goethe-Universität Frankfurt, D-60438 Frankfurt
am Main, Germany
2. Laboratory
for Neutron Scattering and Imaging, Paul Scherrer Institute, CH-5232 Villigen, Switzerland
3. Department
for Quantum Matter Physics, University of Geneva, CH-1211 Geneva, Switzerland
4. Department
of Chemistry and Biochemistry, University of Bern, CH-3012 Bern, Switzerland