Evidence of complete fusion in the sub-barrier O+U reaction

Nishio, Katsuhisa; Ikezoe, Hiroshi; Nagame, Yuichiro; Asai, Masato; Tsukada, Kazuaki; Mitsuoka, Shinichi; Tsuruta, Kaoru; Sato, Kenichiro; Lin, C. J.; Osawa, Takaaki*

Physical Review Letters, 93(16), p.162701_1 - 162701_4, 2004/10

https://doi.org/10.1103/PhysRevLett.93.162701

The fission fragment angular distributions for reactions using actinide targets such as O+U show anomalously large anisotropy than the prediction of the transition state model. To interprete this phenomenon, the orientation dependent quasi-fission model was proposed. As the U has prolate deformation, the interaction of O with the U in the sub-barrier region is restricted to the tip collisions. Hinde et al. interpreted that the anomalously large angular anisotropy is due to the quasi-fission, that is the complete fusion is not achieved in the sub-barrier region. The presence (or absence) of the complete fision is found by measuring the evaporation residue cross sections. We measured the evaporation residue cross sections for O+U by using the O beams supplied by the JAERI-tandem accelerator. As a result, complete fusion was observed in the sub-barrier region and no significant fusion hindrace was observed.