摘要
基于β衰变的费米理论,提出一个计算原子核β衰变寿命且不含自由参数的经验公式.通过引入奇偶效应、壳效应以及同位旋依赖,新提出的经验公式显著改进了对原子核β衰变寿命的预言精度.对于寿命小于1s的原子核,新经验公式的预言结果与实验寿命常用对数的均方根偏差降至 0.220,这比不含自由参数的经验公式提高约 54%,甚至优于目前已有的其他经验公式和微观的准粒子无规相位近似方法.在未知核区,新经验公式预言的轻核区原子核的β衰变寿命一般短于各微观模型的预言结果,而其预言的重核区原子核的β衰变寿命与各微观模型预言结果基本一致.进一步采用新经验公式预言了核素图上丰中子原子核的β衰变寿命,为r-过程的模拟提供了寿命输入.
Abstract
Nuclear β-decay half-lives play an important role not only in nuclear physics,but also in astrophysics.The β-decay half-lives of many nuclei involved in the astrophysical rapid neutron-capture(r-process)still cannot be measured experimentally,so the theoretical predictions of nuclear β-decay half-lives are inevitable for r-process studies.Theoretical models for studying the nuclear β-decay half-lives include the empirical formula,the gross theory,the quasiparticle random phase approximation(QRPA),and the shell model.Compared with other theoretical models of β-decay half-lives,the empirical formula has high computational efficiency,and its prediction accuracy can be improved by introducing more and more physical information.In this work,an empirical formula without free parameters is proposed to calculate the nuclear β-decay half-lives based on the Fermi theory of β decay.By including the pairing effect,the shell effect,and the isospin dependence,the newly proposed empirical formula significantly improves the accuracy of predicting the nuclear β-decay half-life.For the nuclei with half-lives less than 1 second,the root-mean-square deviation of the common logarithms of the nuclear β-decay half-life predicted by the new empirical formula from the experimental data decreases to 0.220,which is improved by about 54%compared with that by the empirical formula without free parameters,even better than those by other existing empirical formulas and microscopic QRPA approaches.In the unknown region,the nuclear β-decay half-lives predicted by the new empirical formula are generally shorter than those predicted by the microscopic models in the light nuclear region,while those predicted by the new empirical formula in the heavy nuclear region are generally in agreement with those predicted by the microscopic models.The half-lives of neutron-rich nuclei on the nuclear chart are then predicted by the new empirical formula,providing nuclear β-decay half-life inputs for the r-process simulations.
基金项目
国家自然科学基金(12375109)
国家自然科学基金(11875070)
国家自然科学基金(11935001)
安徽省高等学校自然科学研究重点项目(2023AH 050095)
维普
万方数据