In a collaborative effort, researchers from institutions including the University of Tokyo, the National Institute for Fusion Science in Japan, and the University of York in the UK have made significant strides in nuclear physics with implications for various fields, including energy. The team, led by Hunter Staiger and Naoki Kimura, employed extreme ultraviolet (EUV) spectroscopy to study highly charged ions (HCIs) of lutetium (Lu) and ytterbium (Yb). Their findings were recently published in the journal Physical Review Letters.
The researchers focused on determining the nuclear charge radius difference between Lu and Yb with high precision. They achieved this by measuring the transition energies in Na- and Mg-like charge states of these elements confined in an electron-beam ion trap. The energy shifts observed were directly sensitive to nuclear-size effects, allowing the team to extract meV-level energy shifts. By comparing these experimental results with state-of-the-art relativistic many-body perturbation theory, the researchers developed a generalized framework to propagate uncertainties arising from nuclear deformation and surface diffuseness.
The study combined data from Na- and Mg-like ions, yielding consistent radius differences and demonstrating the robustness of both the experimental calibration and theoretical predictions. To determine absolute isotopic radii, the team performed a generalized least-squares optimization. This analysis incorporated their HCI constraints along with optical-isotope-shift data and muonic-atom results. The findings established that the charge radius of the lutetium isotope 175Lu is smaller than that of the ytterbium isotope 174Yb, resolving a long-standing anomaly in rare-earth nuclear systematics.
The recommended value for the charge radius of 175Lu is 5.291(11) femtometers, which reduces the uncertainty of the Lu radius by a factor of three compared to previous electron-scattering results. This research highlights the power of EUV spectroscopy of HCIs as a method for precision nuclear-structure studies in heavy, deformed nuclei. The techniques developed here pave the way for future investigations of isotonic and isoelectronic sequences, including radioactive nuclides and higher-Z systems.
For the energy sector, this research contributes to a deeper understanding of nuclear structure, which is fundamental to various applications, including nuclear energy and medical imaging. The precise determination of nuclear charge radii can enhance the accuracy of models used in nuclear reactors and other energy-related technologies. Additionally, the advanced spectroscopic techniques developed in this study can be applied to improve the analysis of nuclear materials, ensuring safer and more efficient energy production.
Source: Physical Review Letters
This article is based on research available at arXiv.