1. Department of Physics, University of Puerto Rico, San Juan, Puerto Rico 00936, USA
2. School of Electrical Engineering and Computer Science, Ohio University, Athens, Ohio 45701-2979, USA
3. Department of Chemistry, University of Puerto Rico, San Juan, Puerto Rico 00936, USA
4. Wihuri Physical Laboratory, Department of Physics and Astronomy, University of Turku, Turku FI-20014, Finland
5. Department of Engineering, Norfolk State University, 700 Park Avenue, Norfolk, Virginia 23504, USA