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arXiv 1910.03335nucl-th
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有限温度下丰中子$N=50$核对恒星电子俘获的解除阻塞

Unblocking of stellar electron capture for neutron-rich $N=50$ nuclei at finite temperature

Alan A. Dzhioev, K. Langanke, G. Martínez-Pinedo, A. I. Vdovin, Ch. Stoyanov

备注：
Published version
发表信息：
Phys. Rev. C 101, 025805 (2020)
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摘要：

我们已经计算了富中子$N=50$核（$^{78}$ Ni，$^{82}$ Ge，$^{86}$ Kr，$^{88}$ Sr）在热QRPA方法中的电子俘获率，在温度$T=0$，对应于基态的俘获，并在$T=10$ GK（0.86 MeV），这是一个典型的温度下，$N=50$核是丰富的超新星崩溃期间。在最近的实验中，我们发现没有伽莫夫-泰勒（GT $_+$）的强度在低激发能量，$E<7$兆电子伏，所造成的泡利阻塞诱导的$N=50$壳间隙。在天体物理学相关的温度下，这种泡利阻挡的GT $_+$强度被克服的热激发整个$Z=40$质子和$N=50$中子壳层间隙，导致相当大的GT贡献的电子捕获。在高密度下，$N=50$核对恒星电子捕获很重要，禁戒跃迁对捕获率有显著的贡献。我们的研究结果表明，富中子的$N=50$核不作为电子捕获的障碍，在超新星坍缩。

英文摘要：

We have calculated electron capture rates for neutron-rich $N=50$ nuclei ($^{78}$Ni, $^{82}$Ge, $^{86}$Kr, $^{88}$Sr) within the Thermal QRPA approach at temperatures $T=0$, corresponding to capture on the ground-state, and at $T=10$ GK (0.86 MeV), which is a typical temperature at which the $N=50$ nuclei are abundant during a supernova collapse. In agreement with recent experiments, we find no Gamow-Teller (GT$_+$) strength at low excitation energies, $E<7$ MeV, caused by Pauli blocking induced by the $N=50$ shell gap. At the astrophysically relevant temperatures this Pauli blocking of the GT$_+$ strength is overcome by thermal excitations across the $Z=40$ proton and $N=50$ neutron shell gaps, leading to a sizable GT contribution to the electron capture. At the high densities, at which the $N=50$ nuclei are important for stellar electron capture, forbidden transitions contribute noticeably to the capture rate. Our results indicate that the neutron-rich $N=50$ nuclei do not serve as an obstacle of electron capture during the supernova collapse.

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