FSU Research Challenges Nuclear Magnetism Theory | Titanium-50 Study Reveals New Insights

Researchers at Florida State University have challenged a long-standing explanation regarding the origin of magnetism in atomic nuclei. A new study examining titanium-50 nuclei indicates that the traditional model of spin-flip excitations does not fully account for magnetic behavior in this isotope. The findings, published in Physical Review Letters on March 31, 2026, suggest that scientists may need to rethink fundamental assumptions about nuclear magnetism.

Understanding the structure of the atomic nucleus is critical for research with implications ranging from astrophysics to practical applications like medical imaging and data storage. Atoms serve as the building blocks of the universe, found in the air, water, and stars. For decades, current nuclear models have treated protons and neutrons as individual particles occupying fixed energy levels. The prevailing theory posited that magnetic strength is largely generated by spin-flip excitations, where particles change the orientation of their spin as they jump between levels.

Challenging Established Models

The research team, utilizing the John D. Fox Superconducting Linear Accelerator Laboratory at Florida State University, conducted experiments that revealed discrepancies in these established models. Associate Professor Mark Spieker, a co-author on the multi-institution study, explained the limitation of the current theoretical framework.

What current models propose is that magnetic strength is largely generated by spin-flip excitations, that means when flipping proton or neutron spins from up to down between so-called spin-orbit partner orbitals. For the first time, we showed that this type of spin-flip cannot be the only mechanism that generates nuclear magnetism.

Associate Professor Mark Spieker

Advanced computer modeling had previously predicted that the spin-flip mechanism was mainly responsible for magnetic strengths, or signals, in atomic nuclei. However, the Florida State University experiments showed something unexpected. Nuclear excited states that clearly displayed the neutron spin-flip structure were not the ones producing the strongest magnetic signals. This indicated that having more of the neutron spin-flip structure did not automatically result in a stronger magnetic effect.

Experimental Methodology

To reach these conclusions, the researchers conducted a neutron-transfer experiment at the John D. Fox Superconducting Linear Accelerator Laboratory. They used the facility’s Tandem Van de Graaff Accelerator to direct a deuteron beam at a thin foil of titanium-49. A deuteron is a nucleus made of a proton and a neutron. During the reaction, the neutron from the beam was transferred to the titanium-49, producing titanium-50 and leaving a residual proton.

Scientists utilized the Super-Enge Split-Pole Spectrograph at the Fox Lab to measure the different angles at which the proton was emitted during the reaction. This measurement allowed them to analyze how the neutron was transferred to the titanium-49. Associate Professor Spieker used an analogy to describe the process of excitation energy.

You could say that the deuteron beam hits the titanium-49, transfers a neutron, and in this process kicks it up a set of stairs. Depending on the nucleus, that set of stairs looks very different. With the spectrograph, You can measure how high the different steps are. How high we get up the set of stairs depends on the excitation energy that we give to the nucleus.

Associate Professor Mark Spieker

The team combined their experimental results with previously published electron- and proton-scattering data. They also incorporated data from new photon-scattering experiments conducted at collaborating universities. By integrating these diverse data sets, the researchers were able to closely examine how neutrons flip their spin and determine how much those flips contribute to the nucleus’s overall magnetic behavior.

Data Integration and Analysis

The researchers observed that the magnetic signal in their experiments was not of the same strength as models predicted. This discrepancy signaled that additional factors must be contributing to the magnetic signals measured for titanium-50. Bryan Kelly, a graduate student at Florida State University and study co-author, emphasized the necessity of using multiple data sources to validate the findings.

Without combining all these data sets, the story cannot be stitched together cleanly. Seeing the other magnetic excitations, that the other probes are sensitive to, allowed us to conclude that the spin-flip mechanism between spin-orbit partners is not the sole factor of magnetic strength generation.

Bryan Kelly

The study’s results challenge long-standing assumptions about the magnetic behavior of nuclei. Improving the scientific understanding of the structure of atomic nuclei will help refine current models used across nuclear physics and astrophysics. It will assist in linking these models with those used in high-energy physics. Such combined efforts between different fields of physics lead to a better understanding of the building blocks of ordinary matter that shape the universe.

Future Research Directions

Developing a better understanding of the universe has potential applications for society and progress, as all ordinary matter is made of atomic nuclei. In future studies, the researchers plan to examine what accounts for the unexplained magnetism in titanium-50. The team noted that magnetic strength measurements alone are insufficient to understand excited states of nuclei.

This research showed that we cannot rely on magnetic strength measurements alone to understand excited states of nuclei. Magnetic strength is spread out across several nuclear states and understanding why will require further investigations of the nucleus.

Bryan Kelly

Researchers from Florida State University, the Technical University of Darmstadt in Germany, and the Triangle Universities Nuclear Laboratory in North Carolina at Duke University contributed to this study. The research was supported by the U.S. National Science Foundation, the U.S. Department of Energy Office of Science, the German Research Foundation, the Institute of Atomic Physics in Romania, the Romanian Ministry of Research, and the Romanian Government.