We investigate the angular momentum removal from fission fragments (FFs) through neutron and $\gamma$-ray emission, finding that about half the neutrons are emitted with angular momenta $\ge 1.5\hslash$ and that the change in angular momentum after the emission of neutrons and statistical $\gamma$ rays is significant, contradicting usual assumptions. Per fission event, in our simulations, the neutron and statistical $\gamma$-ray emissions change the spin of the fragment by $3.5-5\hslash$, with a large standard deviation comparable to the average value. Such wide angular momentum removal distributions can hide any underlying correlations in the fission fragment initial spin values. Within our model, we reproduce data on spin measurements from discrete transitions after neutron emissions, especially in the case of light FFs. The agreement further improves for the heavy fragments if one removes from the analysis the events that would produce isomeric states. Finally, we show that while in our model the initial FF spins do not follow a sawtoothlike behavior observed in recent measurements, the average FF spin computed after neutron and statistical $\gamma$ emissions exhibits a shape that resembles a sawtooth. This suggests that the average FF spin measured after statistical emissions is not necessarily connected with the scission mechanism as previously implied.

中文翻译：

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裂变碎片衰变期间中子和γ射线发射的角动量去除

我们研究了从裂变碎片 (FF) 中通过中子和 $\gamma$-射线发射，发现大约一半的中子以角动量发射 $\ge 1.5\hslash$ 以及中子发射后角动量的变化和统计 $\gamma$射线很重要，与通常的假设相矛盾。每个裂变事件，在我们的模拟中，中子和统计$\gamma$-射线发射改变碎片的自旋 $3.5-5\hslash$，具有与平均值相当的大标准偏差。如此宽的角动量去除分布可以隐藏裂变碎片初始自旋值中的任何潜在相关性。在我们的模型中，我们再现了中子发射后离散跃迁的自旋测量数据，尤其是在轻 FF 的情况下。如果从分析中去除会产生异构状态的事件，那么重片段的一致性会进一步提高。最后，我们表明，虽然在我们的模型中，初始 FF 自旋不遵循最近测量中观察到的锯齿状行为，但在中子和统计之后计算的平均 FF 自旋$\gamma$排放物呈现出类似于锯齿的形状。这表明在统计发射后测量的平均 FF 自旋不一定与先前暗示的断裂机制有关。