1. University of Ngaoundere, Faculty
of Science, P.O. Box 454, Ngaoundere, Cameroon
2. Fundamental Physics Lab, Graduate
Training Unit in Physics and Engineering Sciences, Faculty of Science,
University of Douala, P.O. Box 24157, Douala, Cameroon
3. University of Maroua, P.O. Box
46, Maroua, Cameroon
4. Laboratoire
de Spectroscopie
Atomique et Moléculaire, Faculté des Sciences de Tunis,
Université de Tunis El Manar, Campus Universitaire 1060, Tunis,
Tunisia