1. Department of Physics; Obafemi Awolowo University; Ile-Ife 220005 Nigeria
2. International Centre for Theoretical Physics Strada Costiera 11; 34151 Trieste Italy
3. School of Chemistry and Physics; University of KwaZulu Natal Pietermaritzburg; P Bag X01 Scottsville 3209 South Africa
4. Centre for Non-Conventional Energy Resources 14-Vigyan Bhawan; University of Rajasthan; Jaipur-04 India
5. Centre for Energy research and Development; O.A.U; Ile-Ife 220005 Nigeria
6. Federal College of Education Kotangora; Niger State Nigeria