1. Institute of Physics, University of Rostock, Albert-Einstein-Str. 23-24, 18059 Rostock, Germany
2. Department of Chemistry, Faculty of Science, Cairo University, Giza, Egypt
3. Chemistry Department, Faculty of Science, King Abdulaziz University, P.O. Box 80203, Jeddah 21589, Saudi Arabia
4. Department of Chemistry, Faculty of Science, Benha University, P.O. Box 13518, Benha, Egypt