β-decay spectroscopy of 27S
β-decay spectroscopy of 27S
复制标题
S-27 的 β 衰变光谱
DOI：
10.1103/physrevc.99.064312
复制
发表时间：
2019-06-10
影响因子：
3.1
通讯作者：
Zhang, H. Q.
中科院分区：
文献类型：
--
作者：
Sun, L. J.;Xu, X. X.;Zhang, H. Q.
背景：β衰变能谱为新星和x射线爆发观测数据的精确建模提供了宝贵的核物理输入，并为远离稳定线的壳模型理论提供了严格的测试。由于缺乏实验数据，S-27的衰变机制十分复杂。目的：从实验上约束热核Si-26(p，γ)P-27的反应速率，并探索S-27和Na-27衰变中可能存在的镜面不对称性。方法：用双面硅条探测器结合高纯锗探测器收集S-27的离子，使正电子、质子、电子、电子等电子能谱变化不均匀。结果：得到了关键的3/2(+)共振的精确共振能量和伽马与质子部分宽度之比，从而确定了主要基于实验约束的Si-26(p，伽马)P-27反应速率。测定了S-27的半衰期、在S-27的β衰变中占据的P-27态的激发能、β馈入强度、对数FT值和伽莫-泰勒跃迁强度。构造了一个更完整的S-27 P衰变方案，并将其与镜像核Na-27的β衰变以及考虑了单粒子能量漂移和二体矩阵元约化的壳层模型计算结果进行了比较。结论：在0.1GK附近，本工作产生的新的Si-26(p，γ)P-27反应速率比反应速率库中推荐的速率低两个数量级。还为观察到S-27和Na-27的伽莫夫-泰勒相变的镜面不对称性提供了实验证据。采用与弱束缚质子1S(1/2)轨道相关的修正的U.S.相互作用的壳模型计算，合理地描述了S-27的衰变性质。
Background: beta-decay spectroscopy provides valuable nuclear physics input for accurate modeling of nova and x-ray burst observables and a stringent test for shell-model theories far from the stability line. The decay scheme of S-27 is complicated and far from being understood due to a lack of experimental data prior to this work.Purpose: We aim to experimentally constrain the thermonuclear Si-26(p, gamma)P-27 reaction rate and to probe the possible mirror asymmetry in S-27 and Na-27 decays.Method: The S-27 ions were collected by double-sided silicon strip detectors operating in conjunction with high-purity germanium detectors, so the positrons, protons, and gamma rays emitted in the decay were measured simultaneously.Results: The precise resonance energy and the ratio between gamma and proton partial widths of the key 3/2(+) resonance were obtained, thereby determining the Si-26(p, gamma)P-27 reaction rate based mainly on experimental constraints. The half-life of S-27, the excitation energies, beta-feeding intensities, log ft values, and Gamow-Teller transition strengths for the states of P-27 populated in the beta decay of S-27 were determined. A more complete S-27 P-decay scheme was constructed and compared to the beta decay of mirror nucleus Na-27 and to the shell-model calculations with the universal sd (USD) Hamiltonian taking into account the shift of single-particle energies and the reduction of two-body matrix elements.Conclusions: This work yields a new Si-26(p, gamma)P-27 reaction rate two orders of magnitude lower than the rate recommended in the reaction rate libraries at around 0.1 GK. Experimental evidence for the observation of mirror asymmetries for the Gamow-Teller transitions of S-27 and Na-27 is also provided. The shell-model calculations using a modified USD interaction related to the weakly bound proton 1s(1/2) orbit give a reasonable description of the decay properties of S-27.