1. Graduate School of Science, Hiroshima University, Higashi-Hiroshima 739-8526, Japan
2. Gunung Sari RT.02, RW.24 Kelurahan Ngringo, Kecamatan Jaten, Kabupaten Karanganyar, Jawa Tengah 57731, Indonesia
3. Department of Physics, Universitas Jenderal Soedirman, Karangwangkal Purwokerto 53123, Indonesia
4. Department of Physics, Universitas Gadjah Mada, Bulaksumur Yogyakarta 55281, Indonesia