GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt, Germany.
Department Chemie, Johannes Gutenberg-Universität Mainz, Mainz, Germany.
Nature. 2024 Oct;634(8036):1075-1079. doi: 10.1038/s41586-024-08062-z. Epub 2024 Oct 30.
The quantum-mechanical nuclear-shell structure determines the stability and limits of the existence of the heaviest nuclides with large proton numbers Z ≳ 100 (refs. ). Shell effects also affect the sizes and shapes of atomic nuclei, as shown by laser spectroscopy studies in lighter nuclides. However, experimental information on the charge radii and the nuclear moments of the heavy actinide elements, which link the heaviest naturally abundant nuclides with artificially produced superheavy elements, is sparse. Here we present laser spectroscopy measurements along the fermium (Z = 100) isotopic chain and an extension of data in the nobelium isotopic chain (Z = 102) across a key region. Multiple production schemes and different advanced techniques were applied to determine the isotope shifts in atomic transitions, from which changes in the nuclear mean-square charge radii were extracted. A range of nuclear models based on energy density functionals reproduce well the observed smooth evolution of the nuclear size. Both the remarkable consistency of model prediction and the similarity of predictions for different isotopes suggest a transition to a regime in which shell effects have a diminished effect on the size compared with lighter nuclei.
量子力学核壳结构决定了质子数 Z≳100 的最重核素的稳定性和存在极限（参考文献）。壳效应还会影响原子核的大小和形状，这一点可以通过对较轻核素的激光光谱研究得到证实。然而，关于重锕系元素的电荷半径和核矩的实验信息却很少，这些信息将最重的天然丰度核素与人工生产的超重元素联系起来。在这里，我们沿着镄（Z=100）同位素链进行了激光光谱测量，并在关键区域扩展了钔同位素链（Z=102）的数据。我们采用了多种生产方案和先进技术来确定原子跃迁中的同位素位移，从中提取出核均方电荷半径的变化。一系列基于能量密度泛函的核模型很好地再现了核大小的平滑演化。模型预测的显著一致性以及不同同位素预测的相似性表明，与较轻的原子核相比，壳效应对尺寸的影响减弱，进入了一个新的状态。
