Unexpected inhibition of fusion in nucleus–nucleus collisions
Unexpected inhibition of fusion in nucleus–nucleus collisions
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DOI：
10.1038/35093069
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发表时间：
2001-09
期刊：
影响因子：
64.8
通讯作者：
A. Berriman;D. Hinde;M. Dasgupta;C. Morton;R. D. Butt;J. Newton
中科院分区：
文献类型：
--
作者：
A. Berriman;D. Hinde;M. Dasgupta;C. Morton;R. D. Butt;J. Newton
自然界中没有发现的不稳定的重原子核可以通过两个稳定的原子核融合而产生，这个过程类似于带电液滴的碰撞。最近，几个原子序数为114的超重原子核的形成。)和116(参考文献))是通过重核聚变实现的。这类系统的静电能量非常大(这就是超重原子核不稳定的原因)，所以尽管两个原子核最初可能会被核势俘获，而不是融合，但在将质量转移到较轻的原子核后，它们几乎总是分离。这种被称为准裂变的过程可以抑制核聚变好几个数量级。了解这种抑制可能是形成更多超重元素的关键。从理论上讲，抑制是可以预测的。和参考文献)，当射弹和靶核的电荷乘积Z1Z2大于约1,600。在这里，我们报道了与Z1Z2的三个聚变反应的测量，大约是这个值的一半，每个都形成了21688Ra。我们发现了令人信服的与模型无关的证据，证明了聚变的抑制和准裂变的存在。这些结果与核聚变和裂变的标准图景中的解释不符。
Unstable heavy atomic nuclei not found in nature can be created by fusing two stable nuclei, in a process analogous to colliding charged droplets of liquid. Recently, the formation of a handful of super-heavy nuclei with atomic numbers 114 (ref. ) and 116 (ref. ) has been achieved by fusion of heavy nuclei. The electrostatic energy of such systems is very large (which is the reason super-heavy nuclei are unstable), so although the two nuclei may initially be captured by the nuclear potential, rather than fusing, they almost always separate after transfer of mass to the lighter nucleus. This process, called quasi-fission,, can inhibit fusion by many orders of magnitude. Understanding this inhibition may hold the key to forming more super-heavy elements. Theoretically, inhibition is predicted (ref. and references therein) when the productZ1Z2of the charges of the projectile and target nuclei is larger than about 1,600. Here we report measurements of three fusion reactions withZ1Z2around half this value, each forming21688Ra. We find convincing model-independent evidence both of inhibition of fusion, and of the presence of quasi-fission. These results defy interpretation within the standard picture of nuclear fusion and fission.