1. Department of Physics, California Polytechnic State University, San Luis Obispo, California 93407, USA
2. Department of Chemistry, Illinois Institute of Technology, Chicago, Illinois 60616, USA
3. Department of Physics, North Central College, Naperville, Illinois 60540, USA
4. Materials Measurement Science Division, National Institute of Standards and Technology (NIST), Gaithersburg, Maryland 20899, USA
5. Department of Physics, University of South Florida, Tampa, Florida 33620, USA