1. Department of Physics, University of Texas at Dallas, 800 West Campbell Road, Richardson, Texas 75080, USA
2. Advanced Imaging Research Center, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, Texas 75390, USA
3. National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32310, USA
4. Department of Chemistry, University of Texas at Dallas, 800 West Campbell Road, Richardson, Texas 75080, USA