1. Department of Theoretical Physics, Faculty of Sciences, Russian Friendship University, 3 Ordjonikidze, Moscow 117923, Russia
2. Department of Physics, Faculty of Sciences and Techniques, Abdou Moumouni University, 10662 Niamey, Niger
3. Department of Mathematics and Computer Science, Faculty of Sciences and Techniques, Abdou Moumouni University, 10662 Niamey, Niger