[1] Univ Maroua, Fac Sci, Dept Phys, POB 46, Maroua, Cameroon
[2] Univ Ngaoundere, Fac Sci, Dept Phys, Quantum Theory & Applicat Unit, POB 454, Ngaoundere, Cameroon
[3] Univ Tunis Manar, Fac Sci Tunis, Lab Spect Atom Mol & Applicat, Campus Univ, Tunis 1060, Tunisia
[4] Univ Free State, Dept Chem, POB 339, ZA-9300 Bloemfontein, South Africa