[1] Univ Wisconsin, Dept Phys, Madison, WI 53706 USA
[2] Ecole Polytech Fed Lausanne, Inst Phys Appl, CH-1015 Lausanne, Switzerland
[3] CNR, Inst Struttura Mat, I-00133 Rome, Italy
[4] Univ Wisconsin, Ctr Synchrotron Radiat, Dept Phys, Stoughton, WI 53589 USA
[5] ELMITEC GmbH, D-38678 Clausthal Zellerfeld, Germany