1. Institute of Nuclear Sciences, Hacettepe University, 06800 Ankara, Turkey
2. Current address: Department of Nanoscience and Nanotechnology, Faculty of Arts and Science, Mehmet Akif Ersoy University, 15030 Burdur, Turkey
3. Physics Division, National Center for Theoretical Sciences, Hsinchu 30013, Taiwan
4. Institute of Nuclear Sciences, Hacettepe University, 06800 Ankara, Turkey, e-mail: metasgin@gmail.com