发表机构
University of the West of Scotland; TRIUMF; University of British Columbia; Simon Fraser University; University of North Carolina, Chapel Hill; Triangle Universities Nuclear Laboratory; Duke University（西苏格兰大学; 特利昂姆夫国家粒子加速器中心; 不列颠哥伦比亚大学; 西蒙菲莎大学; 北卡罗来纳大学教堂山分校; 三角大学核实验室; 杜克大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
通过测量$^{224}$Ra低激发负宇称态寿命，独立验证了其八极集体性，并确认了强烈抑制的内禀偶极矩，为核结构模型提供了精确基准。
AI 中文摘要
核素$^{224}$Ra是八极形变以及反射不对称核中增强的Schiff矩理论描述的关键基准。虽然库仑激发测量已确立了$^{224}$Ra中强烈的八极集体性，但理论模型预测其内禀电偶极矩应被宏观与微观贡献之间的抵消强烈抑制。在TRIUMF-ISAC进行了$^{224}$Fr的$\beta$衰变后布居的低激发$J^\pi = 1^-_1$和$3^-_1$态的直接快定时测量。利用GRIFFIN阵列的LaBr$_3$(Ce)探测器，获得了平均寿命$\tau(1^-_1) = 444(6)$~ps和$\tau(3^-_1) = 460(18)$~ps。相应的约化跃迁概率与库仑激发推断的值一致，但以显著提高的精度确定。这些结果为$^{224}$Ra中与八极集体性相关的电磁矩阵元提供了独立验证，并确认了$D_0 \simeq 0.032~e\mathrm{fm}$的强烈抑制的内禀偶极矩。因此，本测量为用于Schiff矩解释和未来非零电偶极矩搜索的核结构模型提供了严格的实验基准。
英文摘要
The nucleus $^{224}$Ra is a key benchmark for octupole deformation and for theoretical descriptions of enhanced Schiff moments in reflection-asymmetric nuclei. While Coulomb-excitation measurements have established strong octupole collectivity in $^{224}$Ra, theoretical models predict that its intrinsic electric-dipole moment should be strongly quenched by a cancellation between macroscopic and microscopic contributions. Direct fast-timing measurements of the low-lying $J^π= 1^-_1$ and $3^-_1$ states populated following the $β$-decay of $^{224}$Fr at TRIUMF-ISAC were performed. Using the LaBr$_3$(Ce) detectors of the GRIFFIN array, mean lifetimes of $τ(1^-_1) = 444(6)$~ps and $τ(3^-_1) = 460(18)$~ps were obtained. The corresponding reduced transition probabilities agree with values inferred from Coulomb excitation, but are determined with substantially improved precision. These results provide an independent validation of the electromagnetic matrix elements associated with octupole collectivity in $^{224}$Ra and confirm a strongly-quenched intrinsic dipole moment of $D_0 \simeq 0.032~e\mathrm{fm}$. The present measurements therefore provide a stringent experimental benchmark for nuclear-structure models used in the interpretation of Schiff moments and future searches for non-zero electric dipole moments.
Comments6 pages, 5 figures
