D. Tahir Department of Physics, Hasanuddin University,Tamalanrea, Makassar 90245, Indonesia Indonesia
H.J. Kang Department of Physics, Chungbuk National University, Cheongju, 361-763 Korea Korea, Republic of
S. Tougaard Department of Physics, Chemistry and Pharmacy, Southern Denmark University, DK-5230 Odense M. Denmark Denmark