1. Department of Physics , Faculty of Science, University of Bamenda , Bambili P.O. Box 39 , Cameroon
2. Department of Physics , Faculty of Science, University of Maroua , Maroua P.O. Box 814 , Cameroon
3. Department of Chemistry , Computational Chemistry Group, Faculty of Science, University of Mauritius , Réduit 80837 Mauritius
4. Department of Chemical Sciences , Centre for Natural Product Research, University of Johannesburg , Doornfontein , Johannesburg 2028 , South Africa
5. Department of Physics , Higher Teacher's Training College, University of Maroua , Maroua P.O. Box 46 , Cameroon
6. Department of Physics , Faculty of Science, University of Ngaoundéré , Ngaoundéré P.O. Box 454 , Cameroon
7. Laboratory of Fundamental Physics, Faculty of Science, University of Douala , Douala P.O. Box 24157 , Cameroon