According to a message on the website of the Institute of Modern Physics, Chinese Academy of Sciences on April 4, the research team of heavy nuclei from the Institute of Modern Physics, Chinese Academy of Sciences, in collaboration with partners, successfully synthesized a new nuclide protactinium-210 for the first time using the China Accelerator Facility for Heavy Element Research (CAFE2). This nuclide is the most neutron-deficient protactinium isotope known so far. The relevant research results were published in "Nature Communications" on May 29.
It was introduced that the synthesis and study of new nuclides are frontier hotspots in atomic nuclear physics research, which have significant meaning for exploring the existence limit of atomic nuclei, revealing new physical phenomena, and deepening the understanding of the structure of matter. However, in the extremely neutron-deficient actinide nucleus region, the production cross-section of new nuclides is extremely low (at the picobarn level), and their lifetimes are extremely short (milliseconds or even microseconds), posing huge challenges to experimental synthesis and research.
The research team used calcium-40 beams provided by the China Accelerator Facility for Heavy Element Research (CAFE2) to bombard lutetium-175 targets, successfully synthesizing the new nuclide protactinium-210 beyond the proton drip line through fusion-evaporation reactions on the gas-filled recoil spectrometer (SHANS2), and successfully measured the alpha decay energy and half-life of this nuclide.
Alpha decay energy spectrum measured in the experiment and two-dimensional coincidence scatter plot of parent-daughter nucleus alpha particle energy
Combining existing experimental data, the team expanded the systematicity of alpha decay properties of nuclides near the proton drip line in the heavy nucleus region and tested the predictions of theoretical models for the properties of atomic nuclei far from beta stability lines. Based on its non-forbidden alpha decay characteristics, the study suggested the spin-parity of the ground state of protactinium-210 as (3⁺), a conclusion supported by large-scale shell model and particle number conserving projected shell model theoretical calculations. In addition, based on the measured proton separation energy, the study provided experimental evidence for the absence of the Thomas-Ehrman shift in protactinium-210.
New generation gas-filled recoil spectrometer (SHANS2)
Original article: https://www.toutiao.com/article/7512353435921007113/
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