Effects of nuclear orientation on fusion and fission in the reaction using U target nucleus

アクチノイド原子核を用いた反応の融合及び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; 永目 諭一郎 ; 大槻 勤*; 廣瀬 健太郎*; Hofmann, S.*

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

We have measured the (1) evaporation residue (ER) cross-sections for Si, S + U and (2) fission fragment mass distributions for Si,S, Ar. Measurement of ER cross-section was carried out at GSI by using the velocity filter SHIP. Measurement of fission fragment mass distribution was made by using the JAEA tandem accelerator. In the reaction Si + U, the ER cross-section for Sg(5n) suggested no fusion hindrance at above-barrier energy, whereas the one for Sg(4n) suggested competition between fusion and 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.