Liu Q, Febbraro M, deBoer R J, Aguilar S, Boeltzig A, Chen Y, Couder M, Görres J, Lamere E, Lyons S, Macon K T, Manukyan K, Morales L, Pain S, Peters W A, Seymour C, Seymour G, Toomey R, Vande Kolk B, Weaver J, Wiescher M
The Joint Institute for Nuclear Astrophysics, Department of Physics, Notre Dame, Indiana 46556, USA.
Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, USA.
J Phys Chem C Nanomater Interfaces. 2020;101. doi: 10.1103/PhysRevC.101.025808.
Nucleosynthesis in the first generation of massive stars offers a unique setting to explore the creation of the first heavier nuclei in an environment free of impurities from earlier stellar generations. In later generations of massive stars, hydrogen burning occurs predominantly through the CNO cycles, but without the carbon, nitrogen, and oxygen to catalyze the reaction sequence, first stars would have to rely on the inefficient chains for their energy production. Observations of second and third generation stars show pronounced abundances of carbon and oxygen isotopes, which suggests a rapid conversion of the primordial abundances to heavier elements. While the triple-alpha-process primarily facilitates this conversion, there are alternative reaction sequences, such as H(, )Li(, )B(, )N, that may play a significant role. To study such alternate reaction pathways for production of carbon and heavier nuclei, a number of new measurements are needed. In this work, new measurements are reported for the B(, )N reaction, extending the cross section down to 575 keV incident -particle energy. The measurements were made using a state-of-the-art deuterated liquid scintillator and a spectrum unfolding technique. An -matrix analysis was performed in order to facilitate a comparison of the underlying nuclear structure with the reaction measurements. An unexpected upturn is observed in the low-energy factor that indicates the presence of a new low-energy resonance. A revised reaction rate is determined that takes into account the present data as well as other previous measurements from the literature that were previously neglected.
第一代大质量恒星中的核合成提供了一个独特的环境，可用于探索在没有早期恒星世代杂质的环境中首批较重原子核的形成。在后来的大质量恒星世代中，氢燃烧主要通过碳氮氧循环发生，但由于没有碳、氮和氧来催化反应序列，首批恒星将不得不依靠效率较低的反应链来产生能量。对第二代和第三代恒星的观测显示，碳和氧同位素的丰度显著，这表明原始丰度迅速转化为更重的元素。虽然三阿尔法过程主要促进了这种转化，但也有其他反应序列，如H(, )Li(, )B(, )N，可能发挥重要作用。为了研究这种产生碳和更重原子核的替代反应途径，需要进行一些新的测量。在这项工作中，报告了对B(, )N反应的新测量，将截面扩展到入射粒子能量低至575 keV。测量使用了最先进的氘化液体闪烁体和谱展开技术。进行了矩阵分析，以便将潜在的核结构与反应测量结果进行比较。在低能因子中观察到意外的上升，这表明存在一个新的低能共振。确定了一个修正的反应速率，该速率考虑了当前数据以及文献中先前被忽视的其他先前测量结果。
