1. Zernike Institute for Advanced Materials University of Groningen Nijenborgh 4 9747 AG Groningen The Netherlands
2. Present address: Max-Planck-Institut für Festkörperforschung Heisenbergstraße 1 70569 Stuttgart Germany
3. Diamond Light Source Harwell Science and Innovation Campus Didcot OX11 0DE UK
4. Laboratoire de Tectonique Moléculaire UMR Unistra-CNRS 7140 Université de Strasbourg 4 rue BlaisePascal 67070 Strasbourg France