Fusion probabilities in the reactions Ca + U at energies around the Coulomb barrier
西尾 勝久 ; 光岡 真一; 西中 一朗; 牧井 宏之 ; 若林 泰生*; 池添 博; 廣瀬 健太郎*; 大槻 勤*; 有友 嘉浩*; Hofmann, S.*
Nishio, Katsuhisa; Mitsuoka, Shinichi; Nishinaka, Ichiro; Makii, Hiroyuki; Wakabayashi, Yasuo*; Ikezoe, Hiroshi; Hirose, Kentaro*; Otsuki, Tsutomu*; Aritomo, Yoshihiro*; Hofmann, S.*
Fission cross sections and fission fragment mass distributions were measured in the reactions of Ca + U and Ca + U at energies around the Coulomb barrier. Fusion probabilities were calculated based on the fluctuation dissipation model. The measured mass distributions for both reactions showed an asymmetric shape at low incident energies, whereas the distribution changed to a flat shape at higher energies. The variation of the mass distribution is explained by a change of the ratio between fusion and qasifission with nuclear orientation. The calculation reproduced the mass distributions and their energy dependence. The trajectories for fusion-fission were used to determine the fusion probability. Fusion probabilities for both reactions are identical as function of the center-of-mass energy, but they differ when plotted as function of the excitation energy. The calculated evaporation residue cross sections for the reaction Ca + U using a statistical model showed that sub-barrier fusion reaction can be applied to form the element 112.