1. Physik-Institut, Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland.
2. Department of Physics, Chalmers University of Technology, SE-412 96 Göteborg, Sweden.
3. Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala, Sweden.
4. Swiss Light Source, Photon Science Division, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland.
5. Diamond Light Source, Harwell Campus, Didcot, Oxfordshire OX11 0DE, UK.
6. Department of Applied Physics, The University of Tokyo, Tokyo 113-8656, Japan.
7. Max Planck Institute for Solid State Research, 70569 Stuttgart, Germany.
8. Department of Physics, The University of Tokyo, Tokyo 113-0033, Japan.