Abstract

An effective approximation to a fully self-consistent global description of beta-decay properties of nuclei within the theory of finite Fermi systems is presented. It is based on describing the ground state properties within the energy density functional proposed by Fayans and coauthors (DF3) and on the continuum quasiparticle random-phase approximation (CQRPA). The accuracy of global DF3 \(+\) CQRPA calculations is analyzed. For more than 200 (quasi)spherical nuclei with \(Z=18\) to 51 having half-lives in the range of \(T_{1/2}<5\) s, the experimental half-lives and delayed neutrons emission probabilities are described within a factor of two and three, respectively. A comparison is performed with the results of similar calculations based on state-of-the-art self-consistent models : the relativistic spherical RHB \(+\) RQRPA approach and deformed finite-amplitude method (FAM) and HFB \(+\) QRPA approaches, as well as the interacting shell model. A detailed analysis of beta-decay properties in the nickel isotopic chain that were obtained in various calculations allows us for determining basic mechanisms responsible for the sudden shortening of the half-lives that was found experimentally at RIKEN for isotopes heavier than the doubly magic \({}^{78}\)Ni nucleus. These are the contributions of first-forbidden (FF) transitions and multiphonon configurations and spin inversion of the respective ground states. The acceleration effect in question is highly sensitive to the balance of the contributions of Gamow–Teller (GT) and FF transitions to the total beta-decay rate. It is shown that, in nickel isotopes, the ratio of these contributions takes different values before and after the neutron-shell crossing at \(N=50\).

中文翻译：

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基于Fayans泛函的Beta衰减特性的全局计算

摘要

提出了在有限费米系统理论内对核的β衰变性质的完全自洽的全局描述的有效近似。它基于描述Fayans和合著者（DF3）提出的能量密度函数内的基态特性，以及连续体准粒子随机相位近似（CQRPA）。分析了全局DF3 \（+ \） CQRPA计算的准确性。对于超过200个（\）（Z = 18 \）至51的半球形原子核，其半衰期在\（T_ {1/2} <5 \）范围内s，实验半衰期和中子延迟发射概率分别描述为2倍和3倍。基于最新的自洽模型，对相似计算的结果进行了比较：相对论球形RHB \（+ \） RQRPA方法和变形有限振幅方法（FAM）和HFB \（+ \ ） QRPA方法以及交互的外壳模型。通过各种计算对镍同位素链中的β衰变性质进行了详细分析，这使我们能够确定导致半衰期突然缩短的基本机理，该机理是在RIKEN实验中发现的，其同位素比双倍魔幻重。 {} ^ {78} \）镍核。这些是首先禁止（FF）跃迁和多声子构型以及相应基态的自旋反转的贡献。所讨论的加速效果对Gamow-Teller（GT）和FF转换对总β衰减率的贡献的平衡非常敏感。结果表明，在镍同位素中，中子和壳层在\（N = 50 \）穿越之前和之后，这些贡献的比率取不同的值。