1. Institute of Physics, Johannes Gutenberg University Mainz, 55128 Mainz, Germany
2. Max Planck Institute for Polymer Research, 55128 Mainz, Germany
3. Institute for Theoretical Physics, Eberhard Karls Universität Tübingen, 72076 Tübingen, Germany
4. European Synchrotron Radiation Facility, 38043 Grenoble, France