Isotopic distributions were measured for the light fragment group in the transition region from asymmetric to symmetric fission for thermal neutron induced fission of ${}^{239}\mathrm{Pu}$ and ${}^{241}\mathrm{Pu}$ using the novel technology of calorimetric low temperature detectors in combination with the passive absorber method. Nuclear charge distributions were determined for 24 masses in the range $A=89$ to $A=112$ for ${}^{241}\mathrm{Pu}(n_{\mathrm{th}},f)$ for the first time with the LOHENGRIN mass spectrometer. Moving from asymmetric to symmetric fission, known data were supplemented for masses from $A=110$ to $A=112$ for ${}^{241}\mathrm{Pu}(n_{\mathrm{th}},f)$ and from $A=109$ to $A=113$ for ${}^{239}\mathrm{Pu}(n_{\mathrm{th}},f)$. The isotopic yields were used to evaluate the charge polarization $\mathrm{\Delta }Z$ and the proton odd-even effect $\delta p$ with emphasis on the borderline between asymmetric and symmetric fission. This highlighted a virtual shell effect near $Z=44$ which mirrors the effect of the $Z=50$ shell in the complementary heavy fragment group of the two Pu isotopes $(Z=94)$ studied.

中文翻译：

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使用量热低温探测器测定的Pu239,241 近对称裂变的热中子诱导裂变碎片的同位素分布

测量了从不对称裂变到对称裂变的过渡区域中轻碎片群的同位素分布，用于热中子诱导裂变 ${}^{239}浦$ 和 ${}^{241}浦$使用与被动吸收器方法相结合的量热低温检测器的新技术。确定了范围内 24 个质量的核电荷分布$\mathrm{一种}=89$ 到 $\mathrm{一种}=112$ 为了 ${}^{241}浦(n_{日},F)$首次使用 LOHENGRIN 质谱仪。从不对称裂变到对称裂变，已知数据补充了来自$\mathrm{一种}=110$ 到 $\mathrm{一种}=112$ 为了 ${}^{241}浦(n_{日},F)$ 并从 $\mathrm{一种}=109$ 到 $\mathrm{一种}=113$ 为了 ${}^{239}浦(n_{日},F)$. 同位素产率用于评估电荷极化$\mathrm{\Delta }Z$ 和质子奇偶效应 $\delta 磷$强调不对称裂变和对称裂变之间的边界。这突出了附近的虚拟壳效果$Z=44$ 这反映了效果 $Z=50$ 两个 Pu 同位素的互补重片段组中的壳 $(Z=94)$ 学习了。