1. II. Physikalisches Institut, Universität zu Köln, D-50937 Cologne, Germany
2. Division of Synchrotron Radiation Research, Lund University, Box 188, SE-22100 Lund, Sweden
3. Elettra-Sincrotrone Trieste S.C.p.A., Strada Statale 14 Km 163.5, I-34149 Trieste, Italy
4. MAX IV Laboratory, Lund University, Box 118, SE-22100 Lund, Sweden