The High Intensity heavy-ion Accelerator Facility (HIAF), which is located in Huizhou, Guangdong Province and began trial operations on July 21, has enabled Chinese scientists to observe an extremely rare isotope, hafnium-153. The observation marks the first physics result achieved during HIAF's commissioning phase, highlighting the facility's capability to explore the boundaries of the nuclear landscape.
The study was published in Science Bulletin, and was led by the Institute of Modern Physics (IMP) of the Chinese Academy of Sciences (CAS), 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.
Exploring new isotopes and determining the limits of nuclear existence are frontiers of nuclear physics. Located in the neutron-deficient heavy nuclear region, hafnium-153 offers a unique window into the evolution of nuclear structure and the limits of nuclear stability. Its observation and precise measurement provide critical information for testing nuclear models and the understanding of nuclear structure.
HIAF is a world-class next-generation heavy-ion accelerator. In this experiment, a bismuth-209 primary beam, provided by HIAF's Booster Ring, was delivered onto a graphite target to produce radioactive nuclei through projectile fragmentation reactions. The cocktail beam was purified and transported by the HIgh rigidity Radioactive Ion Beam Line (HIRIBL) before being injected into the Spectrometer Ring (SRing), where isochronous mass spectrometry was employed for precision measurements.
Despite an extremely low production cross section, the researchers observed a total of ten hafnium-153 ions. The results indicated that hafnium-153 is a bound or weakly bound isotope, consistent with the predictions from various nuclear mass models.
Concurrently, the Radioactive Isotope Beam Factory (RIBF) at RIKEN in Japan also independently reported the observation of hafnium-153. These two independent measurements provide mutual confirmation and highlight the significance of this isotope in nuclear physics research.
According to the researchers, the detection of hafnium-153 showcases the integrated capabilities of HIAF. The high-intensity heavy-ion beams enhance the production of rare isotopes; high-performance HIRIBL enables efficient separation of the nuclei of interest; and SRing's isochronous mass spectrometry provides single-ion sensitivity for precise identification and measurement of rare nuclei.
This study not only marks an advance in probing the limits of nuclear existence, but also opens the door to broader scientific exploration at HIAF. With further improvements in beam intensity and experimental efficiency, HIAF is expected to play an increasingly important role in the discovery of new isotopes and the investigation of nuclear properties under extreme conditions.
