1. Centre for Atomic Molecular Physics and Quantum Optics (CEPAMOQ), University of Douala, Douala, Cameroon
2. Department of Physics, Faculty of Sciences, University of Douala, Douala, Cameroon
3. National Radiation Protection Agency, Yaounde, Cameroon
4. Atomic and Nuclear Spectroscopy, Archeometry, University of Liège, Liege, Belgium