1. Department of Physics, Oakland University, Rochester, Michigan 48309, United States
2. Deutsches GeoForschungsZentrum, Section 3.6, Telegrafenberg, 14473 Potsdam, Germany
3. Deutsches GeoForschungsZentrum, Section 3.5, Telegrafenberg, 14473 Potsdam, Germany
4. Carl Zeiss AG, Carl-Zeiss-Strasse 22, 73447 Oberkochen, Germany
5. Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, P. O. Box 808, L-350, Livermore, California 94550, United States