New spectroscopy method enables direct comparisons of nuclear sizes across heavy elements
The size of a nucleus (nuclear charge radius) is an important physical quantity that reflects the arrangement of protons and neutrons within the nucleus. Particularly in deformed nuclei, such as those of rare-earth elements, examining changes in the charge radius can deepen our understanding of nuclear structure and nuclear deformation.
An international research team, led by the National Institute for Fusion Science, has developed a new spectroscopy method that allows for direct comparisons of nuclear sizes across heavy elements. This breakthrough is particularly significant for understanding the arrangement of protons and neutrons within a nucleus, especially in deformed nuclei like those found in rare-earth elements.
The team utilized the Tokyo-EBIT experimental apparatus at the University of Electro-Communications to generate highly charged ions (HCIs) of lutetium (Lu) and ytterbium (Yb), which enabled them to measure the nuclear radii with unprecedented precision. By analyzing the shifts in energy levels of these HCIs, the researchers were able to convert the observed differences in emission line energies into differences in nuclear radii.
Their findings reveal that the nucleus of lutetium, which has an odd number of protons, is slightly smaller than that of ytterbium, which has an even number of protons. This resolution to the long-standing debate about the odd-even staggering in the atomic-number dependence of nuclear radii in the rare-earth region marks a significant advancement in nuclear physics, demonstrating that the new method can effectively evaluate nuclear radii for direct comparisons between different elements.
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