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arXiv 1203.4669nucl-thastro-ph.HEastro-ph.SR
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丰质子核$^{57}$ Zn的Gamow-Teller强度分布及其天体物理意义

Gamow-Teller strength distribution in proton-rich nucleus $^{57}$Zn and its implications in astrophysics

Jameel-Un Nabi, Muneeb-Ur Rahman

备注：
9 pages, 5 figures, 1 table
发表信息：
Astrophysics and Space Science, 332, 309-317 (2011)
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摘要：

伽莫夫-特勒（GT）跃迁在恒星核心坍缩形成II型超新星的过程中起着重要作用。在质子-中子准粒子无规相近似（pn-QRPA）理论框架下，计算了$^{57}$ Zn基态和激发态的B（GT）强度分布.没有实验插入（通常在B（GT）强度函数的其他pn-QRPA计算中进行）来检查模型对富质子核的性能。计算出的基态B（GT）强度分布与测量结果吻合良好，并显示出与早期报道的壳模型计算的差异。pn-QRPA模型再现了测得的低位强度$^{57}$锌更好地相比，在大规模壳模型计算中使用的KB 3G相互作用。恒星的弱速率对子体$^{57}$ Cu中这些低激发态的位置和结构很敏感。产生这种核的主要机制是rp过程，并且被认为在坍缩超大质量恒星的动力学中很重要。结合能和激发能的微小变化可以导致对合成富质子同位素的预测的显著修改。将$^{57}$ Zn上的$β^{+}$ -衰变和电子捕获（EC）速率与Fuller、Fowler和Newman（FFN）的开创性工作进行比较。pn-QRPA计算的$β^{+}$ -衰减速率通常与FFN计算结果一致。然而，在高恒星温度下，计算的$β^{+}$衰变率几乎是FFN率的一半。另一方面，对于rp过程的条件下，计算出的电子捕获（$β^{+}$ -衰变）率大于FFN率超过2倍（1.5），可能有有趣的天体物理后果。

英文摘要：

Gamow-Teller (GT) transitions play a preeminent role in the collapse of stellar core in the stages leading to a Type-II supernova. The B(GT) strength distributions for ground and excited states of $^{57}$Zn are calculated in the domain of proton-neutron Quasiparticle Random Phase Approximation (pn-QRPA) theory. No experimental insertions were made (as usually made in other pn-QRPA calculations of B(GT) strength function) to check the performance of the model for proton-rich nuclei. The calculated ground-state B(GT) strength distribution is in good agreement with measurements and shows differences with the earlier reported shell model calculation. The pn-QRPA model reproduced the measured low-lying strength for $^{57}$Zn better in comparison to the KB3G interaction used in the large-scale shell model calculation. The stellar weak rates are sensitive to the location and structure of these low-lying states in daughter $^{57}$Cu. The primary mechanism for producing such nuclei is the rp-process and is believed to be important in the dynamics of the collapsing supermassive stars. Small changes in the binding and excitation energies can lead to significant modifications of the predictions for the synthesis of proton rich isotopes. The $β^{+}$-decay and electron capture (EC) rates on $^{57}$Zn are compared to the seminal work of Fuller, Fowler and Newman (FFN). The pn-QRPA calculated $β^{+}$-decay rates are generally in good agreement with the FFN calculation. However at high stellar temperatures the calculated $β^{+}$-decay rates are almost half of FFN rates. On the other hand, for rp-process conditions, the calculated electron capture ($β^{+}$-decay) rates are bigger than FFN rates by more than a factor 2 (1.5) and may have interesting astrophysical consequences.

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