1. Fundamental Physics Laboratory, Department of Physics, Faculty of Science, University of Douala 1 , Box 24, 157 Douala, Cameroon
2. Department of Physics, Pontifical Catholic University of Rio de Janeiro, Rua Marquês de São Vicente 2 , 225–22451–900 Gávea, Rio de Janeiro, Brazil
3. Faculty of Technology, Rio de Janeiro State University (FAT UERJ) 3 , 27.537-000 Resende, Rio de Janeiro, Brazil