太阳系中^(205)Pb同位素起源的研究

The Origin of^(205)Pb Isotope in the Solar System

短寿命核素可以提供高精度的年代学信息,对研究太阳系的形成和演化非常重要。^(205)Pb作为独一无二的纯s-过程短寿命核素,它的半衰期为17.0(9)My,衰变子体为^(205)Tl。^(205)Pb-^(205)Tl衰变系统可以作为研究太阳系中^(205)Pb起源的时钟。本工作利用ENDF/B-Ⅷ.0数据库中最新的核反应截面评价数据,计算了不同质量和金属性的AGB星演化后期^(205)Pb与204Pb的同位素产额比,通过银河化学演化模型进一步计算得到了早期太阳系中^(205)Pb与^(204)Pb同位素丰度比。并将理论预测结果与太阳系早期陨石的实验测量结果进行了比较。结果显示,太阳系中^(205)Pb同位素主要来源于质量为1.5~2 M_(☉)且金属性Z=0.004~0.008范围的AGB星。

Short-lived radionuclides can provide high-precision chronological information,which is very important in the study of the formation and evolution of the solar system.^(205)Pb is a short-lived nuclide with a half-life of 17.0(9)My and is classified as a pure s-process nucleus.The^(205)Pb-^(205)Tl decay system can be used as a clock to study the origin of^(205)Pb in the solar system.In this paper,the isotope yield ratios of^(205)Pb and^(204)Pb for AGB stars with different masses and metallicities were calculated using the latest evaluation data of nuclear reaction cross sections in ENDF/B-Ⅷ.0 database.The isotopic abundance ratios of^(205)Pb and^(204)Pb in the early solar system were further calculated by the Galactic chemical evolution model.The theoretical result is compared with the experimental measurement result from meteorites produced in the early solar system.It is concluded that the^(205)Pb nuclide in the solar system may be created during the evolution of AGB stars with masses of 1.5~2.0 M_☉and metallicities in the range Z=0.004~0.008.