Nucleosynthesis is a complex process in astro-nuclear evolution. In this work, we constructed a directed, multi-layer, nuclear reaction network, using the substrate-product method from a thermonuclear reaction database, JINA REACLIB. The network contained four layers, namely $n$-, $p$-, $h$- and $r$-, which correspond to the types of reactions involved in neutrons, protons, $^4$He and the remaining atomic particles, respectively. The degree values (i.e. numbers of reactions), for three layers of $n$-, $p$-, and $h$-, have a significant correlation with one another, and their topological structures exhibit a similar regularity. However, the $r$-layer has a more complex topological structure compared to the other layers; thus, its correlation of degree values with the other three layers is not as strong as that seen in the other layers. To analyze the motif structure of the nuclear reaction network, we used the software package “mfinder. We identified the most frequent reaction patterns of the interconnections that occurred amongst the different nuclides. This work provides a novel approach to investigating the nuclear reaction network that prevails in the astrophysical context.

Network structure of thermonuclear reactions in nuclear landscape

Nuclear reaction rate ($\lambda$) is a significant factor in the process of nucleosynthesis. A multi-layer directed-weighted nuclear reaction network in which the reaction rate as the weight, and neutron, proton, $^4$He and the remainder nuclei as the criterion for different reaction-layers is for the first time built based on all thermonuclear reactions in the JINA REACLIB database. Our results show that with the increase of the stellar temperature ($T_{9}$), the distribution of nuclear reaction rates on the $R$-layer network demonstrates a transition from unimodal to bimodal distributions. Nuclei on the $R$-layer in the region of $\lambda = [1,2.5\times10^{1}]$ have a more complicated out-going degree distribution than the one in the region of $\lambda = [10^{11},10^{13}]$, and the number of involved nuclei at $T_{9} = 1$ is very different from the one at $T_{9} = 3$. The redundant nuclei in the region of $\lambda = [1, 2.5\times10^{1}]$ at $T_{9} = 3$ prefer $(\gamma,p)$ and $({\gamma,\alpha})$ reactions to the ones at $T_{9}=1$, which produce nuclei around the $\beta$ stable line. This work offers a novel way to the big-data analysis on nuclear reaction network at stellar temperatures.

Reaction Rate Weighted Multilayer Nuclear Reaction Network

Nucleosynthesis is a complex process in astro-nuclear evolution. In this work, we construct a directed multi-layer nuclear reaction network using the substrate-product method from a thermonuclear reaction database, JINA REACLIB. The network contains four layers, namely $n$-, $p$-, $h$- and $r$, corresponding to the reaction types involved in neutrons, protons, $^4$He and the remainder, respectively. The degree values (i.e. numbers of reactions) for three layers of n-, p- and h- have a significant correlation with one another, and their topological structures exhibit a similar regularity. However, the $r$-layer has a more complex topological structure than others and has less correlation with the other three layers. A software package named `mfinder' is employed to analyze the motif structure of the nuclear reaction network. We thus identify the most frequent reaction patterns of interconnections occurring among different nuclides. This work provides a novel approach to study the nuclear reaction network prevailing in the astrophysical context.

Reaction rate weighted multilayer nuclear reaction network

Theoretical uncertainties of (d,$$^{3}$$He) and ($$^{3}$$He,d) reactions owing to the uncertainties of optical model potentials

This paper presents the results of a study that compares CTOM, a microscopic optical model potential (OMP), which is an optical model co-created by the China Nuclear Data Center & Tuebingen University, to CH89, which is a typical phenomenological OMP. The respective OMPs were tested by applying them to the modelling of nucleon elastic scattering and (d, p) transfer reactions involving 14C, 36S, and 58Ni targets at both low and relatively high energies. The results demonstrated that although both potentials successfully accounted for the angular distributions of both the elastic scattering and transfer cross sections, the absolute values of the transfer cross sections calculated using CTOM were approximately 25% larger than those calculated using CH89. This increased transfer cross sections allowed CTOM to produce single particle strength reduction factors for the three reactions that were consistent with those extracted from (e, e′ p) reactions as well as with more recent (p, 2p) and (p, pn) reactions. Notch tests suggested that nucleon elastic scattering and transfer reactions are sensitive to different regions of the OMP; accordingly, phenomenological OMPs, which are constrained only by elastic scattering cross sections, may not be sufficient for nucleon transfer reactions. Therefore, we suggest that microscopic OMPs, which reflect more theoretical considerations, should be preferred over phenomenological ones in calculations of direct nuclear reactions.

YiPing Xu

Papers

What kind of optical model potentials should be used for deuteron stripping reactions