1. Department of Physical and Macromolecular Chemistry, Faculty of Science, Charles University, Hlavova 8, 128 43 Prague 2, Czech Republic
2. Institut Max von Laue-Paul Langevin (ILL), 71 avenue des Martyrs, CS 20156, F-38042 Grenoble Cedex 9, France
3. NMR Laboratory, Faculty of Science, Charles University, Hlavova 8, 128 43 Prague 2, Czech Republic