Effects of nuclear orientation on fusion and fission process for reactions using uranium target nuclei

ウランを標的核とする反応の融合・核分裂過程における原子核の変形効果

西尾 勝久   ; 池添 博; 光岡 真一; 西中 一朗; 牧井 宏之   ; 渡辺 裕*; 永目 諭一郎 ; 大槻 勤*; 廣瀬 健太郎*; Hofmann, S.*

Nishio, Katsuhisa; Ikezoe, Hiroshi; Mitsuoka, Shinichi; Nishinaka, Ichiro; Makii, Hiroyuki; Watanabe, Yutaka*; Nagame, Yuichiro; Otsuki, Tsutomu*; Hirose, Kentaro*; Hofmann, S.*

Results on the measurements of (1) evaporation residue (ER) cross-sections for Si, S + U and of (2) fission fragment mass distributions for Si,S, Ar + U will be discussed. Measurement of ER cross-section was carried out at GSI by using the velocity filter SHIP. Measurement of fission fragment mass distributions was made by using the JAEA tandem accelerator. In the reaction Si + U, the ER cross-section for Sg(5n) suggested no fusion hindance at above-barrier energy, whereas the one for Sg(4n) suggested competition between fusion and quasi-fission at sub-barrier energy. This conclusion is consistent with the measured fragment mass distributions, where the asymmetric fission component associated with quasi-fission appears only at sub-barrier energies. In the reaction of S + U, the ER cross-sections for Hs(5n) and Hs(4n, new isotope) suggested fusion hindrance both for above- and sub-barrier energies. With the results of fission fragment mass distributions, it is found that quasi-fission has symmetric fission components when projectile mass is relatively large. We will also discuss the variation of the fragment mass distributions for Si,S, Ar + U.