HIAF’s First Physics Result: 10 Hafnium-153 Ions at the Edge of Nuclear Stability

China’s High Intensity heavy-ion Accelerator Facility (HIAF) has produced and identified hafnium-153 (^153Hf) as its first reported physics result during commissioning. Scientists observed just 10 ions of the extremely neutron-deficient isotope, demonstrating that the new facility can reach rare nuclei near the limits of nuclear existence.

HIAF’s first result in brief

HIAF is located in Huizhou, Guangdong Province, China, and began trial operations on July 21, 2026. The facility is designed to create, separate and precisely measure rare radioactive nuclei—work that helps researchers map how far atomic nuclei can exist before becoming unstable.

The hafnium-153 study was led by the Chinese Academy of Sciences’ Institute of Modern Physics. Collaborators included the University of Chinese Academy of Sciences, GSI Helmholtz Centre for Heavy Ion Research, the University of Cologne, East China University of Technology and the Advanced Energy Science and Technology Guangdong Laboratory. The result was published as a short communication in Science Bulletin.

Why hafnium-153 is significant

Hafnium-153 belongs to the neutron-deficient region of heavy nuclei, where the balance between protons and neutrons becomes increasingly difficult to maintain. Before this experiment, the isotope had not been reported. Establishing its existence and measuring its mass gives nuclear physicists a new data point for testing mass models and studying how nuclear structure changes toward the edge of stability.

The measurement indicates that ^153Hf is bound or weakly bound, in agreement with predictions from several nuclear-mass models. That agreement does not settle every question about the isotope, but it provides an important experimental check on theories used to predict nuclei that are difficult—or not yet possible—to observe directly.

How HIAF produced and identified the isotope

The experiment began with a beam of bismuth-209 accelerated to 836.66 MeV per nucleon in HIAF’s Booster Ring. The beam struck a graphite target, triggering projectile-fragmentation reactions that produced a mixture of radioactive nuclei.

That mixture then had to be filtered and measured. The HIRIBL high-energy radioactive-ion beamline separated and transported the reaction products to the SRing storage and spectrometer ring. Time-of-flight detectors helped distinguish candidate nuclei, while isochronous mass spectrometry provided the precision measurement needed to identify hafnium-153. In total, the team recorded 10 ^153Hf ions.

The challenge was not simply making hafnium-153, but recognizing it among far more common reaction products. Its estimated production cross section was at the picobarn scale, meaning that the isotope was created exceptionally rarely. HIAF’s intense primary beam, high-resolution fragment separation and single-ion-sensitive mass spectrometry had to work together to produce a credible identification.

Independent observation at RIKEN

Around the same time, researchers at Japan’s Radioactive Isotope Beam Factory (RIBF) at RIKEN independently reported observing ^153Hf. The two observations mutually reinforce the isotope’s identification and reduce the uncertainty that can accompany a result based on only a handful of detected ions.

Independent confirmation is especially valuable for nuclei produced at extremely low rates. In this case, the agreement between the HIAF and RIBF observations strengthens the result while giving researchers a firmer basis for using hafnium-153 in comparisons with nuclear theory.

What the result says about HIAF

The discovery is an early performance demonstration rather than the endpoint of HIAF’s scientific program. It shows that the facility’s accelerator, radioactive-beam transport, fragment-separation and precision mass-measurement capabilities can be coordinated to study nuclei that are both rare and short-lived.

As HIAF’s beam intensity and experimental efficiency improve, the facility’s experimental reach is expected to increase by roughly two orders of magnitude. That could enable the discovery of additional isotopes, more demanding tests of nuclear-mass models and measurements of nuclear properties under increasingly extreme proton–neutron imbalance.

Hafnium-153 therefore matters for two reasons: it is a new—and exceptionally difficult—nucleus to produce and identify, and it is a practical demonstration that HIAF is ready to investigate the less-explored boundaries of the nuclear landscape.