1. Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley CA 94720, U.S.A.
2. Randall Laboratory of Physics, University of Michigan, Ann Arbor, MI 48109-1120, U.S.A.
3. Los Alamos National Laboratory, Los Alamos, NM 87545, U.S.A.
4. National High Magnetic Field Laboratory and Department of Physics, Florida State University, Tallahassee, FL 32306, U.S.A.