Abstract The synthesis of new superheavy elements beyond oganesson (Z=118) requires fusion reactions with projectile nuclei with proton numbers larger than that of 48Ca (Z=20), which has been successfully employed for the synthesis of elements with Z=112-118. In such reactions, fusion is drastically hindered by fast non-equilibrated dynamical processes. Attempts to produce nuclei with Z=120 using the 64Ni+238U, 58Fe+244Pu, 54Cr+248Cm, and 50Ti+249Cf reactions have been made, which all result in larger Coulomb forces than for 48Ca-induced reactions, but no discovery has been confirmed to date. In this work, mass and angle distributions of fission fragments from these reactions have been measured with large angular coverage to aid in selection of the most promising projectile-target combination that would favor fusion. The results yield information on reaction contact times, with the longest exhibited by 50Ti+249Cf.

中文翻译：

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元素Z=120合成的Zeptosecond接触时间

摘要 合成超重元素 oganesson (Z=118) 需要与质子数大于 48Ca (Z=20) 的弹核发生聚变反应，已成功用于合成 Z=112-118 的元素. 在这种反应中，快速的非平衡动力学过程极大地阻碍了聚变。已经尝试使用 64Ni+238U、58Fe+244Pu、54Cr+248Cm 和 50Ti+249Cf 反应产生 Z=120 的核，这些反应都导致比 48Ca 诱导反应更大的库仑力，但没有发现确认至今。在这项工作中，来自这些反应的裂变碎片的质量和角度分布已在大角度覆盖范围内进行测量，以帮助选择最有希望的有利于融合的弹丸-目标组合。