Tin is the chemical element with the largest number of stable isotopes. Its complete proton shell, comparable with the closed electron shells in the chemically inert noble gases, is not a mere precursor to extended stability; since the protons carry the nuclear charge, their spatial arrangement also drives the nuclear electromagnetism. We report high-precision measurements of the electromagnetic moments and isomeric differences in charge radii between the lowest 1/2⁺, 3/2⁺, and 11/2⁻ states in ^117–131Sn, obtained by collinear laser spectroscopy. Supported by state-of-the-art atomic-structure calculations, the data accurately show a considerable attenuation of the quadrupole moments in the closed-shell tin isotopes relative to those of cadmium, with two protons less. Linear and quadratic mass-dependent trends are observed. While microscopic density functional theory explains the global behaviour of the measured quantities, interpretation of the local patterns demands higher-fidelity modelling.

锡是具有最大数量稳定同位素的化学元素。其完整的质子壳，与化学惰性惰性气体中的封闭电子壳相比，不仅是扩展稳定性的前兆；由于质子带有核电荷，因此它们的空间排列也驱动了核电磁。我们报告了在^117–131中最低的1/2 ⁺，3/2 ⁺和11 ^{/ 2-}态之间的电磁矩和电荷半径的异构体差的高精度测量通过共线激光光谱法获得的锡。在最先进的原子结构计算的支持下，数据准确地显示出闭壳锡同位素中的四极矩相对于镉具有相当大的衰减，少了两个质子。观察到线性和二次质量相关趋势。微观密度泛函理论解释了被测量的整体行为，而局部模式的解释则需要更高保真度的建模。