Fermium-255 Nucleus Shape Measured Precisely
Laser spectroscopy reveals a strongly prolate fermium-255 nucleus and corrects a previously tabulated magnetic dipole moment.
Updated on Nov. 3, 2026 in Nuclear
Researchers determined the shape of the fermium-255 nucleus using laser spectroscopy and found it is strongly prolate, with 100 protons and 155 neutrons. The results, published May 15, 2026 in Physical Review Letters, also show the magnetic dipole moment differs from previously tabulated values.
Why it matters
The earlier technology could not resolve the fine nuclear details needed for accurate structure measurements. The findings could improve predictions of the stability of superheavy elements that have yet to be discovered.
Samples contained tens of millions to about one billion fermium atoms, heated to roughly 1,000 degrees Celsius for laser analysis. The magnetic dipole moment measurement differs from previously tabulated values, and the implications for superheavy element predictions remain untested.
The players
Johannes Gutenberg University Mainz
A German public research university where RISIKO separator analysis for the study was performed.
Oak Ridge National Laboratory
A U.S. Department of Energy research facility that carried out the initial neutron irradiation of transuranium material.
Institute Laue-Langevin
A research institute in Grenoble, France, that performed additional neutron irradiation for the fermium-255 samples.
The details
Researchers studied how electrons interact with the nucleus, producing small differences in atomic energy levels that precise lasers can detect. Fermium-255 was produced by neutron irradiation of transuranium material at Oak Ridge National Laboratory, followed by further irradiation at the Institute Laue-Langevin in France.
Timeline
More than 20 years ago: scientists first observed fermium atomic energy levels.
Months before the experiments: neutron irradiation of transuranium material began at Oak Ridge.
May 15, 2026: the study was published in Physical Review Letters.
The Big Picture
The measured results agree closely with modern nuclear theories developed in France and Germany, supporting their predictions for heavy nuclei. The work also adds fine-grained structural data that heavy-element theory has lacked for this isotope.
The findings could sharpen predictions of which superheavy elements might be stable enough to study, guiding future attempts to create them. Any practical application remains years away and depends on further experiments and theory.
The takeaway
Precise laser measurements can reveal nuclear shapes that older methods could not resolve, improving the foundations for predicting elements not yet discovered. Such refinements matter because they test the theories scientists rely on at the edge of the periodic table.
Further reading
Explore more on Nuclear research and the atomic structure of heavy elements.
More information
Read the full Physical Review Letters fermium-255 study on the journal's site.
Source note: This article includes information reported by SciTechDaily.
