Strong one-neutron emission from two-neutron unbound states in β decays of the r -process nuclei Ga86,87
Strong one-neutron emission from two-neutron unbound states in β decays of the r -process nuclei Ga86,87
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r 过程核 Ga86,87 β 衰变中两个中子未束缚态的强单中子发射
DOI：
10.1103/physrevc.100.031302
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发表时间：
2019
影响因子：
3.1
通讯作者：
Algora, A.
中科院分区：
文献类型：
--
作者：
Yokoyama, R.;Grzywacz, R.;Rasco, B. C.;Brewer, N.;Rykaczewski, K. P.;Dillmann, I.;Tain, J. L.;Nishimura, S.;Ahn, D. S.;Algora, A.
在日本理化研究所西那中心的放射性同位素束流工厂（RIBF）使用高效率中子计数器阵列（BRIKEN）测量了87 Ga同位素衰变的延迟单中子和双中子分支比。在衰变中首次观测到双中子发射，分支比分别为和。首次测定了单中子分支比和29(4)ms的半衰期。与之前的研究相比，测量的分支比例也更精确。对两者的观察都是出乎意料的，并且被解释为在双中子非束缚激发态中占主导地位的单中子发射的标志。为了解释实验结果，采用壳模型和Hauser-Feshbach统计模型计算了延迟粒子和射线发射概率。该模型框架再现了实验结果。壳层模型本身的预测量明显大于衰变的预测量，因此有必要调用统计描述来成功地解释这一观察结果。我们的新结果证明了中子发射的统计描述对于多中子发射体衰变特性预测的相关性和重要性，并且它必须包含在过程建模中。
-delayed one-neutron and two-neutron branching ratiosandhave been measured in the decay ofto 87 Ga isotopes at the Radioactive-Isotope Beam Factory (RIBF) at the RIKEN Nishina Center using a high-efficiency array ofneutron counters (BRIKEN). Two-neutron emission was observed in the decay offor the first time and the branching ratios were measured to be, and, respectively. One-neutron branching ratio ofand half-life of 29(4) ms were measured for the first time. The branching ratios ofwere also measured to beandwith better precision than a previous study. The observation thatfor bothwas unexpected and is interpreted as a signature of dominating one-neutron emission from the two-neutron unbound excited states in. In order to interpret the experimental results, shell-model and Hauser-Feshbach statistical model calculations of delayed particle and-ray emission probabilities were performed. This model framework reproduces the experimental results. The shell model alone predictssignificantly larger thanfor thedecay, and it is necessary to invoke a statistical description to successfully explain the observation that. Our new results demonstrate the relevance and importance of a statistical description of neutron emission for the prediction of the decay properties of multineutron emitters and that it must be included in the-process modeling.