In the heaviest elements, the instability of atomic nuclei against spontaneous fission leads to ever shorter nuclear half-lives. Upon falling below a timescale of ${10}^{-14}$ s, the border of existence of isotopes is crossed because this is the timescale on which the formation of atomic shells occurs. Analysis of the experimental data on the spontaneous fission half-lives of Rf isotopes in relation with their expected single-particle orbitals hint at a potentially abrupt decrease in half-lives of unknown neutron-deficient Rf isotopes with neutron numbers $<149$, which suggests that the isotopic border is already almost reached. However, this conjecture, which cannot be explained within the current knowledge, was directly related to uncertainty in the experimental data on ${}^{253}\mathrm{Rf}$. We revisited the decay of ${}^{253}\mathrm{Rf}$ and identified two fission activities, which are attributed to decays of the two different states with half-lives of $12.8_{-3.4}^{+7.0}$ ms and ${44}_{-10}^{+17}\mu \mathrm{s}$. In addition, hitherto unknown $\alpha$ decay in ${}^{253}\mathrm{Rf}$, which is followed by $\alpha$ decay of the new isotope ${}^{249}\mathrm{No}$ with a half-life of ${15}_{-7}^{+74}$ ms, was observed. Based on our new data, no abrupt decreases in half-lives of the neutron-deficient No and Rf isotopes are expected, which is in line with theoretical predictions. Fission half-lives of the two different states in ${}^{253}\mathrm{Rf}$ are benchmark cases for the theoretical description of the single-particle orbital influence on the fission process.

中文翻译：

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缺乏中子的 No 和 Rf 同位素的自发裂变不稳定性：新的 isotopeNo249

在最重的元素中，原子核对自发裂变的不稳定性导致核半衰期越来越短。在低于时间刻度时${10}^{-14}$ s，同位素存在的边界被跨越，因为这是原子壳形成发生的时间尺度。对 Rf 同位素自发裂变半衰期与其预期单粒子轨道相关的实验数据的分析表明，具有中子数的未知中子缺陷 Rf 同位素的半衰期可能突然下降$<149$，这表明已经几乎达到同位素边界。然而，这一猜想在目前的知识范围内无法解释，与实验数据的不确定性直接相关。${}^{253}\mathrm{射频}$. 我们重温了衰败${}^{253}\mathrm{射频}$ 并确定了两种裂变活动，这归因于两种不同状态的衰变，半衰期为 $12.8_{-3.4}^{+7.0}$ 毫秒和 ${44}_{-10}^{+17}\mu \mathrm{秒}$. 此外，至今无人知晓$\alpha$ 衰落 ${}^{253}\mathrm{射频}$，其次是 $\alpha$ 新同位素的衰变 ${}^{249}不$ 半衰期为 ${15}_{-7}^{+74}$女士，被观察到。根据我们的新数据，预计中子缺乏的 No 和 Rf 同位素的半衰期不会突然下降，这与理论预测一致。两种不同状态的裂变半衰期${}^{253}\mathrm{射频}$ 是单粒子轨道对裂变过程影响的理论描述的基准案例。