Scientists from the Institute of Modern Physics (IMP) of the Chinese Academy of Sciences, University of Surrey of UK, and Universidade Federal Fluminense of Brazil have lately made new progress in the study of the production of ⁹⁴Tc nucleus, a Technetium (Tc) isotope, which is one of the promising candidates for the application of medical diagnostics.  

The ⁹⁴Tc has an isomeric state of (2)⁺, namely ⁹⁴Tc^m. With large positron branching ratio and medium positron end-point energy, the ⁹⁴Tc^m is a suitable candidate for Positron Emission Tomography, and regarded as an intriguing alternative to many current popular tracers.  

Various nuclear reactions have been employed in the production of Tc isotopes. However, most of the studies are based on the light-ion-induced reactions，and thus there is a lack of data based on the heavy-ion-induced reactions. 

At Heavy Ion Research Facility in Lanzhou (HIRFL), an experiment with a heavy projectile involved ⁹Be + ⁸⁹Y was conducted by the Superheavy Nuclide and Nuclear Structure group of IMP and their collaborators. Researchers applied the online activation method and the offline measurement technique.  

The isomer yield ratios, defined as the production of isomeric state of (2)⁺ (⁹⁴Tc^m) relative to the ground state of 7⁺ ( ⁹⁴Tc^g), were determined experimentally at different beam energies, using the different characteristic γ-rays from their decays. 

Furthermore, scientists have explored the reaction mechanism by employing a phenomenological approach with a cut-off spin and a spreading parameter. An agreement in the order of magnitude between the experimental data and theoretical predictions has been achieved. Possible factors that may affect the isomer yield ratios, such as the γ-quantum and neutrons emitted during the de-excitation of compound nucleus, were also addressed in this study.   

The study extends information on the reaction mechanisms and production of ⁹⁴Tc, a biologically important nucleus.  

This work was supported by the Youth Innovation Promotion Association of Chinese Academy of Sciences, the Strategic Priority Research Program of Chinese Academy of Sciences, and the National Natural Science Foundation of China.  

The result was published in Physical Review C on November, 12. 

Link to the paper: https://journals.aps.org/prc/abstract/10.1103/PhysRevC.102.054607

Fig. 1 Calculated angular momentum distribution for compound nucleus from fusion of ⁹Be + ⁸⁹Y system at beam energies of 45.9- and 48.1-MeV. The division of population between the ground 7⁺ and isomeric (2)⁺ state at 45.9-MeV is indicated by the blue and red lines. (Image by LI Guangshun)

Fig. 2 Calculated and measured isomer ratios for ⁹⁴Tc formed through ⁹Be + ⁸⁹Y system, assuming different cut-off spin (J_eff) and spreading (δ) values. (Image by LI Guangshun) 

Contact :

LIU Fang

Institute of Modern Physics

Email: fangliu@impcas.ac.cn