垒下熔合裂变中观察到的异常

Anomaly Observed in Subbarrier Fusion-Fission Reactions

测量了１６Ｏ＋２３２Ｔｈ、２３８Ｕ和１９Ｆ＋２３２Ｔｈ近垒和垒下熔合裂变截面以及碎片角分布．包含靶核静态形变的耦合道理论解释了垒下熔合截面增强，预言了复合核系统自旋分布展宽．而实验上观察到的碎片角分布各向异性明显与裂变统计理论的预言不一致．

The fusion-fission cross sections and fragment angular distributions for the systems of 16O+232Th, 16O+238U and 19F+232Th at near-and sub-barrier energies have been measured. The enhancement of fusion-fission cross sections at subbarrier energies is well explained in the framework of coupled-channels theory in which the target static deformations are explicitly taken into account. However, the experimental fragment anisotropies obviously deviate from the predictions of the statistic fission model.