The production of about half of the heavy elements found in nature is assigned to a specific astrophysical nucleosynthesis process: the rapid neutron-capture process ($r$ process). Although this idea was postulated more than six decades ago, the full understanding faces two types of uncertainties or open questions: (a) The nucleosynthesis path in the nuclear chart runs close to the neutron-drip line, where presently only limited experimental information is available, and one has to rely strongly on theoretical predictions for nuclear properties. (b) While for many years the occurrence of the $r$ process has been associated with supernovae, where the innermost ejecta close to the central neutron star were supposed to be neutron rich, more recent studies have cast substantial doubts on this environment. Possibly only a weak $r$ process, with no or negligible production of the third $r$-process peak, can be accounted for, while much more neutron-rich conditions, including an $r$-process path with fission cycling, are likely responsible for the majority of the heavy $r$-process elements. Such conditions could result during the ejection of initially highly neutron-rich matter, as found in neutron stars, or during the fast ejection of matter that has previously experienced strong electron captures at high densities. Possible scenarios are the mergers of neutron stars, neutron-star–black hole mergers, but also include rare classes of supernovae as well as hypernovae or collapsars with polar jet ejecta, and possibly also accretion disk outflows related to the collapse of fast rotating massive stars. The composition of the ejecta from each event determines the temporal evolution of the $r$-process abundances during the “chemical” evolution of the Galaxy. Stellar $r$-process abundance observations have provided insight into and constraints on the frequency of and conditions in the responsible stellar production sites. One of them, neutron-star mergers, was just identified thanks to the observation of the $r$-process kilonova electromagnetic transient following the gravitational wave event GW170817. These observations, which are becoming increasingly precise due to improved experimental atomic data and high-resolution observations, have been particularly important in defining the heavy element abundance patterns of the old halo stars, and thus in determining the extent and nature of the earliest nucleosynthesis in the Galaxy. Combining new results and important breakthroughs in the related nuclear, atomic, and astronomical fields of science, this review attempts to answer the question “How were the elements from iron to uranium made?”

中文翻译：

---

最重元素的起源：快速中子捕获过程

自然界中大约一半的重元素的产生被分配给特定的天体物理核合成过程：快速中子捕获过程（$\mathrm{[R}$处理）。尽管这个想法是在六十多年前提出的，但全面的理解面临两种类型的不确定性或悬而未决的问题：（a）核图中的核合成路径接近中子滴灌线，目前仅可获得有限的实验信息，而且必须强烈依赖于对核特性的理论预测。（b）多年以来，$\mathrm{[R}$这个过程与超新星有关，在超新星中，靠近中子星中心的最内层喷射应该被认为是中子丰富的，最近的研究对这种环境提出了很大的怀疑。可能只有弱者$\mathrm{[R}$ 过程，没有或可以忽略不计的第三次生产 $\mathrm{[R}$可以解释过程峰值，而更多的中子富集条件，包括 $\mathrm{[R}$裂变循环的过程路径，可能是造成大部分重物的原因 $\mathrm{[R}$过程元素。这样的条件可能是在最初释放中子星中发现的高度富含中子的物质的过程中，或者是在先前已经以高密度进行过强电子捕获的物质的快速排出过程中导致的。可能的情况是中子星合并，中子星-黑洞合并，但也包括极少类的超新星以及具有极地射流喷射的超新星或塌缩星，还可能包括与快速旋转的大质量恒星坍塌有关的吸积盘流出。 。每个事件中喷射物的组成决定了喷射物的时间演变$\mathrm{[R}$-银河“化学”演化过程中的过程丰度。恒星$\mathrm{[R}$-过程的丰度观察提供了对负责任的恒星生产地点的频率和条件的了解和约束。其中之一就是中子星合并，这要归功于观察到的$\mathrm{[R}$引力波事件GW170817之后处理千伏电磁瞬变。这些观测结果由于改进的实验原子数据和高分辨率观测结果而变得越来越精确，对于定义旧光晕恒星的重元素丰度模式以及由此确定最早的核合成的范围和性质尤其重要。银河系。本文结合相关的核，原子和天文科学领域的新成果和重要突破，试图回答以下问题：“铁到铀的元素是如何制成的？”