分类： 核科学技术 >> 核科学与技术 提交时间： 2025-06-30
摘要： Exploring the limits of neutron binding in atomic nuclei remains a central focus of nuclear physics. However, the experimental determination of the neutron drip line is challenging because of the minuscule production cross sections of the most neutron-rich isotopes. We investigated the effectiveness of multi-step fragmentation for producing extremely neutron-rich nuclides at relativistic energies. We demonstrate that multi-step fragmentation dominates over single-step fragmentation in thick target experiments and can enhance the yields of drip line nuclei by several orders of magnitude in a realistic experiment using fragment separators. Such enhancements open new possibilities for locating drip lines above sodium, and thus significantly expand the research horizon.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Hao Cheng
Bao-Hua Sun
Li-Hua Zhu
Motohiko Kusakabe
Yun Zheng
Liu-Chun He
Toshitaka Kajino
Zhong-Ming Niu
Tian-Xiao Li
Cong-Bo Li
Dong-Xi Wang
Meng Wang
Guang-Shuai Li
Kang Wang
Lin Song
Ge Guo
Zhi-Yong Huang
Xiu-Lin Wei
Fu-WeI Zhao
Xiao-Guang Wu
摘要： Rare information on photodisintegration reactions of nuclei with mass numbers $A \approx 160$ at astrophysical conditions impedes our understanding of the origin of $p$-nuclei. Experimental determination of the key ($p,\gamma$) cross sections has been playing an important role to verify nuclear reaction models and to provide rates of relevant ($\gamma,p$) reactions in $\gamma$-process. In this paper we report the first cross section measurements of $^{160}$Dy($p,\gamma$)$^{161}$Ho and $^{161}$Dy($p,n$)$^{161}$Ho in the beam energy range of 3.4 - 7.0 MeV, partially covering the Gamow window. Such determinations are possible by using two targets with various isotopic fractions. The cross section data can put a strong constraint on the nuclear level densities and gamma strength functions for $A \approx$ 160 in the Hauser-Feshbach statistical model. Furthermore, we find the best parameters for TALYS that reproduce the A $\thicksim$ 160 data available, $^{160}$Dy($p,\gamma$)$^{161}$Ho and $^{162}$Er($p,\gamma$)$^{163}$Tm, and recommend the constrained $^{161}$Ho($\gamma,p$)$^{160}$Dy reaction rates over a wide temperature range for $\gamma$-process network calculations. Although the determined $^{161}$Ho($\gamma$, p) stellar reaction rates at the temperature of 1 to 2 GK can differ by up to one order of magnitude from the NON-SMOKER predictions, it has a minor effect on the yields of $^{160}$Dy and accordingly the $p$-nuclei, $^{156,158}$Dy. A sensitivity study confirms that the cross section of $^{160}$Dy($p$, $\gamma$)$^{161}$Ho is measured precisely enough to predict yields of $p$-nuclei in the $\gamma$-process.
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