1. Department of Physics; Acharya Nagarjuna University; Nagarjuna Nagar-522 510 A.P India
2. Department of Physics; Kakani Venkata Ratnam College; Nandigama-521 185 A.P. India
3. Bhabha Atomic Research Centre; Chemistry Division; Mumbai-400 085 India
4. Institute of Physics; Jan Dlugosz University; Ul. Armii Krajowej 13/15 Czestochowa-42-201 Poland