Recently, the Institute of Modern Physics of the Chinese Academy of Sciences and its partners synthesized new neutron deficient nuclides osmium-160 and tungsten 156 for the first time, revealing that the shell effect of 82 neutrons is enhanced in extreme neutron deficient nuclides. On February 15th, the relevant research results were published in the Physical Review Letters as recommended by the editor of a highlight article, and were reported online by the Journal of Physics of the American Physical Society.

away from β The evolution of the nuclear shell structure of stable lines is a hot topic in nuclear physics research. Research has shown that traditional magic numbers disappear and new magic numbers appear on the neutron rich side of the nuclide map, which has attracted widespread attention from researchers. In the neutron deficient region, the synthesis of new nuclides is related to α Measurement of decay properties is one of the effective ways to study shell structure and its evolution.

Based on the Lanzhou heavy ion accelerator, this study synthesized two new nuclides, osmium-160 and tungsten 156, through fusion evaporation reaction using an inflatable recoil nuclear spectrometer SHANS. Research has found that osmium-160 (with a neutron number of 84) has α Radioactive, while tungsten 156 (with a neutron count of 82) has β+ Decaying radioactivity. The team measured the concentration of osmium-160 α Properties such as decay particle energy, half-life, and half-life of tungsten 156.

This study found through systematic analysis of new measurement data and existing data that the same neutron element with neutron numbers of 84 and 85 has α The decay reduction width shows a regular decreasing trend from proton numbers of 68 to 76. This indicates that as the atomic number increases, the neutron numbers of 84 and 85 for the same neutron element are α The probability of particle pre formation decreases. Research suggests that the above phenomenon is caused by the enhanced shell effect with a neutron number of 82. This explanation is supported by three different nuclear mass models.

Further research shows that the reason for the enhanced neutron shell effect with a neutron number of 82 is due to the continuous approximation of the possible double magic nucleus - lead-164 (with a proton number of 82 and a neutron number of 82). Although lead-164 is far beyond the proton droplet line, the enhanced shell effect may make it a bound or quasi bound atomic nucleus.

This study provides for the first time a clear understanding of the evolution of a neutron shell with a neutron number of 82 on the side of a neutron deficient nuclide, while also ushering in a new nuclear region for new nuclide research in China.

This work was jointly completed by the Institute of Modern Physics, the Laboratory of Super heavy Nuclei and Nuclear Structure, the University of the Chinese Academy of Sciences, the Guangdong Provincial Laboratory of Advanced Energy Science and Technology, Shandong University, Sun Yat sen University, Guangxi Normal University, the Institute of Theoretical Physics of the Chinese Academy of Sciences, and Tongji University. The research work was supported by the Chinese Academy of Sciences' strategic leading science and technology project, the major project of basic and applied basic research in Guangdong Province, and the National Natural Science Foundation of China.

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The positions of new nuclides osmium-160 and tungsten 156 on the nuclide map.