Open Access

Katsuhisa Nishio, Hiroshi Ikezoe, Sigurd Hofmann, Dieter Ackermann, Stanislav Antalic, Yoshihiro Aritomo, Victor Fernandovich Comas-Lijachev, Christoph E. Düllmann, Alexander Gorshkov, Reimar Graeger, Kouichi Hagino, Sophia Heinz, Julio Antonio Heredia Cardona, Katsuhisa Hirose, Jadambaa Khuyagbaatar, Birgit Kindler, Ivan Kojouharov, Bettina Lommel, Hiroyuki Makii, Rido Mann, Shinichi Mitsuoka, Yuichiro Nagame, Ichiro Nishinaka, Tsutomu Ohtsuki, Andrey G. Popeko, Štefan Šaro, Matthias Schädel, Andreas Türler, Yasuo Wakabayashi, Yosuke Watanabe, Alexander Yakushev, Alexander V. Yeremin

• Fragment mass distributions for fission after full momentum transfer were measured in the reactions of 30Si,34,36 S,31P,40Ar + 238U at bombarding energies around the Coulomb barrier. Mass distributions change significantly as a function of incident beam energy. The asymmetric fission probability increases at sub-barrier energy. The phenomenon is interpreted as an enhanced quasifission probability owing to orientation effects on fusion and/or quasifission. The evaporation residue (ER) cross sections were measured in the reactions of 30Si + 238U and 34S + 238U to obtain information on fusion. In the latter reaction, significant suppression of fusion was implied. This suggests that fission events different from compound nucleus are included in the masssymmetric fragments. The results are supported by a model calculation based on a dynamical calculation using Langevin equation, in which the mass distribution for fusion-fission and quasifission fragments are separately determined.