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arXiv 1906.09258nucl-thnucl-ex
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$^7$ Be和$^7$ Li核在无核壳模型下的连续介质

$^7$Be and $^7$Li nuclei within the no-core shell model with continuum

Matteo Vorabbi, Petr Navrátil, Sofia Quaglioni, Guillaume Hupin

摘要:

$^7$ Be和$^7$ Li核的产生在原始核合成、核天体物理和聚变能产生中起着重要作用。$^3\mathrm{He}(α, γ) ^7\mathrm{Be}$和$^3\mathrm{H}(α, γ) ^7\mathrm{Li}$的辐射俘获过程对于确定早期宇宙中$^7$ Li的丰度和预测导致$^7$ Be和$^8$ B中微子的pp链分支的正确比例是很重要的。本工作中,我们采用无核壳模型连续介质(NCSMC)方法,以手征核子-核子相互作用为唯一输入,研究了$^7$ Be和$^7$ Li的性质,并分析了这些体系形成过程中所涉及的所有二元质量分配. NCSMC是一种适用于轻核的从头计算方法,它提供了对束缚态和散射态的统一描述,因此非常适合于研究具有许多共振和明显簇集的系统,如$^7$ Be和$^7$ Li。我们的计算再现了这两个系统的所有实验已知的状态,并提供了两个宇称的几个新的共振的预测。这些新的可能的共振中的一些是建立在$^6$ Li和$^6$ He的基态上的,并且因此代表稳健的预测。我们没有发现任何共振的p ${+}^6$锂质量分区附近的阈值。另一方面,在$^7$ Li的p ${+}^6$ He质量分配中,我们观察到阈值附近的$S$波共振,在计算的$^6\mathrm{He} (\mathrm{p},γ) ^7\mathrm{Li}$辐射捕获反应的S因子中产生非常明显的峰值,这可能与天体物理学相关,其含义应该被研究。

英文摘要:

The production of $^7$Be and $^7$Li nuclei plays an important role in primordial nucleosynthesis, nuclear astrophysics, and fusion energy generation. The $^3\mathrm{He}(α, γ) ^7\mathrm{Be}$ and $^3\mathrm{H}(α, γ) ^7\mathrm{Li}$ radiative-capture processes are important to determine the $^7$Li abundance in the early universe and to predict the correct fraction of pp-chain branches resulting in $^7$Be versus $^8$B neutrinos. In this work we study the properties of $^7$Be and $^7$Li within the no-core shell model with continuum (NCSMC) method, using chiral nucleon-nucleon interactions as the only input, and analyze all the binary mass partitions involved in the formation of these systems. The NCSMC is an ab initio method applicable to light nuclei that provides a unified description of bound and scattering states and thus is well suited to investigate systems with many resonances and pronounced clustering like $^7$Be and $^7$Li. Our calculations reproduce all the experimentally known states of the two systems and provide predictions for several new resonances of both parities. Some of these new possible resonances are built on the ground states of $^6$Li and $^6$He, and thus represent a robust prediction. We do not find any resonance in the p${+}^6$Li mass partition near the threshold. On the other hand, in the p${+}^6$He mass partition of $^7$Li we observe an $S$-wave resonance near the threshold producing a very pronounced peak in the calculated S factor of the $^6\mathrm{He} (\mathrm{p},γ) ^7\mathrm{Li}$ radiative-capture reaction, which could be relevant for astrophysics and its implications should be investigated.

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