Direct mass measurements above uranium bridge the gap to the island of stability
Direct mass measurements above uranium bridge the gap to the island of stability
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DOI：
10.1038/nature08774
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发表时间：
2010-02-11
期刊：
影响因子：
64.8
通讯作者：
Weber, C.
中科院分区：
文献类型：
--
作者：
Block, M.;Ackermann, D.;Weber, C.
原子的质量包含其所有成分及其相互作用(1)。原子的质量与其组成部分的总和（结合能）之间的差值是爱因斯坦著名关系式 E = mc(2) 的体现。结合能决定了核反应和衰变（从而通过恒星核合成产生元素）可用的能量，并掌握了元素有多重这一基本问题的关键。在具有挑战性的生产实验中已经观察到超重元素(2-4)，但我们目前对这些核素结合能的了解仅基于对其衰变产物的检测。从扩展的衰变链重建引入了不确定性，使得解释变得困难。在这里，我们报告了超铀核素的直接质量测量。这些核素位于质子数-中子数图上锕系元素的最远尖端，代表了通往预测的稳定岛的门户。特别是，我们用潘宁阱质谱仪SHIPTRAP(5)测定了No252-254（原子序数102）的质量值。尽管分钟生产率低于每秒一个原子，但不确定性约为 10 keV/c(2)（表示相对精度为 0.05 p.p.m.）。我们的实验将直接质量测量推进了十个原子序数，且精度没有损失，并在通往稳定岛的途中提供了可靠的锚点。
The mass of an atom incorporates all its constituents and their interactions(1). The difference between the mass of an atom and the sum of its building blocks (the binding energy) is a manifestation of Einstein's famous relation E = mc(2). The binding energy determines the energy available for nuclear reactions and decays (and thus the creation of elements by stellar nucleosynthesis), and holds the key to the fundamental question of how heavy the elements can be. Superheavy elements have been observed in challenging production experiments(2-4), but our present knowledge of the binding energy of these nuclides is based only on the detection of their decay products. The reconstruction from extended decay chains introduces uncertainties that render the interpretation difficult. Here we report direct mass measurements of transuranium nuclides. Located at the farthest tip of the actinide species on the proton number-neutron number diagram, these nuclides represent the gateway to the predicted island of stability. In particular, we have determined the mass values of No252-254 (atomic number 102) with the Penning trap mass spectrometer SHIPTRAP(5). The uncertainties are of the order of 10 keV/c(2) (representing a relative precision of 0.05 p.p.m.), despite minute production rates of less than one atom per second. Our experiments advance direct mass measurements by ten atomic numbers with no loss in accuracy, and provide reliable anchor points en route to the island of stability.