发表机构
University of California, Berkeley; University of Notre Dame; Clemson University（加州大学伯克利分校; 圣母大学; 克莱姆森大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究揭示冷r-过程冻结阶段由动态中子经济性主动塑造，通过出口者-进口者关系及俘获与延迟发射竞争形成峰结构，并指出模型高估$P_n$概率，需理论改进与FRIB实验验证。
AI 中文摘要
标准r-过程模型通常将冻结阶段视为对全局丰度模式的被动、均匀平滑处理。然而，我们证明最终模式实际上是由一种动态的“中子经济性”主动塑造的，这种经济性在自由中子源耗尽后仍持续运作。通过分析冷中子星并合外流，我们识别出一种独特的中子出口者-进口者关系：第二峰区域（$A \sim 130$）较早转变为$\beta$衰变主导状态，充当净出口者，而第三峰（$A \sim 195$）和稀土（$A \sim 164$）区域则保持俘获主导的中子进口者。针对性模拟揭示，最终峰结构源于两种相反力量的竞争：一种是由中子俘获驱动的全局“推力”，将质量移向更重的核素；另一种是$\beta$延迟中子发射产生的局部“拉力”，将物质送回较轻质量。我们确定$^{136}\text{Pd}$、$^{135}\text{Ag}$和$^{130}\text{Ru}$为驱动此经济性的主要出口者，而第三峰精细结构由$N=126$同中子素（Sm至Tb）控制。物理上，这种输运反映了向壳层闭合的基本驱动，其中越过$N=82$闭合壳层的核素通过抛射质量迁移回这一稳定构型，而第三峰中的核素俘获这些再分配的中子以锚定在$N=126$壳层。关键的是，我们的模型在第三峰中产生的奇偶交错相对于太阳数据过度。这一差异表明当前模型可能高估了这些$N=126$核素的$\beta$延迟中子发射概率（$P_n$），凸显它们为理论改进和未来FRIB实验的高优先级目标。
英文摘要
Standard r-process models often treat the freeze-out phase as a passive, uniform smoothing of the global abundance pattern. We demonstrate, however, that the final pattern is instead actively sculpted by a dynamic ``neutron economy'' that operates well after the free neutron source is exhausted. By analyzing cold neutron star merger outflows, we identify a distinct neutron exporter-importer relationship: the second-peak region ($A \sim 130$) transitions early into a $β$-decay dominated regime, acting as a net exporter, while the third-peak ($A \sim 195$) and Rare Earth ($A \sim 164$) regions remain capture-dominated neutron importers. Targeted simulations reveal that the final peak structures emerge from a competition between two opposing forces: a global ``push'' driven by neutron capture shifting mass toward heavier nuclei, and a local ``pull'' from beta delayed neutron emission returning material back toward lighter masses. We identify $^{136}\text{Pd}$, $^{135}\text{Ag}$, and $^{130}\text{Ru}$ as the primary exporters driving this economy, while third-peak fine structure is governed by $N=126$ isotones (Sm to Tb). Physically, this transport reflects a fundamental drive toward shell closure, where nuclei that overshoot the $N=82$ closed shell shed mass to migrate back toward this stable configuration, while nuclei in the third peak capture these redistributed neutrons to anchor themselves at the $N=126$ shell. Crucially, our models overproduce the odd-even staggering in the third peak compared to solar data. This discrepancy suggests current models likely overestimate the $β$-delayed neutron emission probabilities ($P_n$) for these $N=126$ nuclei, highlighting them as high-priority targets for theoretical refinement and future FRIB experiments.
Comments10 pages, 8 figures
