The 12C(α, γ)16O reaction and its implications for stellar helium burning
The 12C(α, γ)16O reaction and its implications for stellar helium burning
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DOI：
10.1103/revmodphys.89.035007
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发表时间：
2017-09-07
影响因子：
44.1
通讯作者：
Uberseder, E.
中科院分区：
文献类型：
--
作者：
deboer, R. J.;Gorres, J.;Uberseder, E.
宇宙中碳和氧的产生是核天体物理学的前沿问题之一。确定这些元素的丰度是我们理解地球生命形成和恒星生命周期的关键。虽然几乎所有不同核合成环境的模型都受到碳和氧产生的影响，但一个关键因素，即12 C（α，γ）O-16反应速率的精确测定，长期以来一直是难以捉摸的。这是由于反应的不可接近性，无论是实验上还是理论上。原子核理论很难计算这个反应速率，因为截面是通过不同的基本原子核机制产生的。同位旋选择规则抑制基态截面的E1分量，产生E1和E2贡献几乎相等幅度的独特情况。在实验上也有很大的挑战。测量已经被推到了最先进技术的极限，这些技术通常只是为了这些测量而开发的。这些数据一直受到未表征的不确定性的困扰，这通常是由于新的测量技术使得不同的结果难以协调。然而，近年来情况有了明显改善，接近10%的预期不确定性水平可能就在眼前。在这篇综述中，总结了目前对这一关键反应的理解。重点主要放在实验工作和反应数据的解释上，但也讨论了理论和天体物理学。主要目的是总结和澄清目前对反应的理解，然后指出改进反应速率测定的方向。
The creation of carbon and oxygen in our Universe is one of the forefront questions in nuclear astrophysics. The determination of the abundance of these elements is key to our understanding of both the formation of life on Earth and to the life cycles of stars. While nearly all models of different nucleosynthesis environments are affected by the production of carbon and oxygen, a key ingredient, the precise determination of the reaction rate of 12C(alpha, gamma)O-16, has long remained elusive. This is owed to the reaction's inaccessibility, both experimentally and theoretically. Nuclear theory has struggled to calculate this reaction rate because the cross section is produced through different underlying nuclear mechanisms. Isospin selection rules suppress the E1 component of the ground state cross section, creating a unique situation where the E1 and E2 contributions are of nearly equal amplitudes. Experimentally there have also been great challenges. Measurements have been pushed to the limits of state-of-the-art techniques, often developed for just these measurements. The data have been plagued by uncharacterized uncertainties, often the result of the novel measurement techniques that have made the different results challenging to reconcile. However, the situation has markedly improved in recent years, and the desired level of uncertainty approximate to 10% may be in sight. In this review the current understanding of this critical reaction is summarized. The emphasis is placed primarily on the experimental work and interpretation of the reaction data, but discussions of the theory and astrophysics are also pursued. The main goal is to summarize and clarify the current understanding of the reaction and then point the way forward to an improved determination of the reaction rate.