标题： 固体样品中$ {}^{229m} \mathrm{Th} $衰变模式的理论评估 显示英文标题

标题： Theoretical evaluation of decay mode of $ {}^{229m} \mathrm{Th} $ in solid samples

摘要： $ {}^{229m} \mathrm{Th} $的激发能非常低，为$ 8.4 \, \mathrm{eV} $；因此，该同位素的衰变模式会根据化学状态发生变化，特别是最外层电子状态。 然而，之前实验中报道的$ \gamma $-射线跃迁的半衰期并不一致。 在本研究中，我们通过 DFT 计算研究了$ {}^{229m} \mathrm{Th} $的化学状态。 基于这些结果，我们评估了每个样品的实验半衰期与$ \mathrm{Th} $电子状态之间的关系。 计算结果表明，离子阱方法、$ \mathrm{Ca} \mathrm{F}_2 $模型和$ \mathrm{Mg} \mathrm{F}_2 $只通过$ \gamma $-射线跃迁衰变，而$ \mathrm{Li} \mathrm{Sr} \mathrm{Al} \mathrm{F}_6 $通过$ \gamma $-射线跃迁衰变，并且有可能通过内转换和电子桥衰变。 显示英文摘要

摘要： The excitation energy of $ {}^{229m} \mathrm{Th} $ is extremely low at $ 8.4 \, \mathrm{eV} $; thus, this isotope exhibits changes in its decay modes depending on the chemical state, specifically the outermost electronic states. However, the reported half-lives of $ \gamma $-ray transition are not consistent among the previous experiments. In this study, we investigate the chemical states of $ {}^{229m} \mathrm{Th} $ by DFT calculations. Based on these results, we evaluate the relationship between the experimental half-life for each sample and the electronic state of $ \mathrm{Th} $. The calculation results indicate that ion trap method, $ \mathrm{Ca} \mathrm{F}_2 $ model and $ \mathrm{Mg} \mathrm{F}_2 $ one decay only via the $ \gamma $-ray transition, whereas $ \mathrm{Li} \mathrm{Sr} \mathrm{Al} \mathrm{F}_6 $ decay via the $ \gamma $-ray transition and has a possibility of decay via internal conversion, and electron bridge.