1. European Center
of Archaeometry, University of Liège, Sart Tilman B15, B-4000 Liège, Belgium
2. Faculty of Sciences, University of Liège, Sart Tilman
B6, B-4000 Liège, Belgium
3. Department of Chemistry, Missouri
University of Science and Technology, University of Missouri, Rolla, Missouri 65409-0010, United States
4. Institut Néel, CNRS and Université Joseph Fourier, BP 166, F-38042
Grenoble Cedex 9, France