The ${}^{13}\mathrm{C}(\alpha ,n){}^{16}\mathrm{O}$ reaction is the main neutron source for the slow-neutron-capture process in asymptotic giant branch stars and for the intermediate process. Direct measurements at astrophysical energies in above-ground laboratories are hindered by the extremely small cross sections and vast cosmic-ray-induced background. We performed the first consistent direct measurement in the range of $E_{\mathrm{c}.\mathrm{m}.}=0.24$ to 1.9 MeV using the accelerators at the China Jinping Underground Laboratory and Sichuan University. Our measurement covers almost the entire intermediate process Gamow window in which the large uncertainty of the previous experiments has been reduced from 60% down to 15%, eliminates the large systematic uncertainty in the extrapolation arising from the inconsistency of existing datasets, and provides a more reliable reaction rate for the studies of the slow-neutron-capture and intermediate processes along with the first direct determination of the alpha strength for the near-threshold state.

Nuclear astrophysics is a rapidly developing interdisciplinary field of research that has received extensive attention from the scientific community since the mid-twentieth century. Broadly, it uses the laws of extremely small atomic nuclei to explain the evolution of the universe. Owing to the complexity of nucleosynthesis processes and our limited understanding of nuclear physics in astrophysical environments, several critical astrophysical problems remain unsolved. To achieve a better understanding of astrophysics, it is necessary to measure the cross sections of key nuclear reactions with the precision required by astrophysical models. Direct measurement of nuclear reaction cross sections is an important method of investigating how nuclear reactions influence stellar evolution. Given the challenges involved in measuring the extremely low cross sections of nuclear reactions in the Gamow peak and preparing radioactive targets, indirect methods, such as the transfer reaction, coulomb dissociation, and surrogate ratio methods, have been developed over the past several decades. These are powerful tools in the investigation of, for example, neutron-capture (n, $$\gamma$$γ ) reactions with short-lived radioactive isotopes. However, direct measurement is still preferable, such as in the case of reactions involving light and stable nuclei. As an essential part of stellar evolution, these low-energy stable nuclear reactions have been of particular interest in recent years. To overcome the difficulties in measurements near or deeply within the Gamow window, the combination of an underground laboratory and high-exposure accelerator/detector complex is currently the optimal solution. Therefore, underground experiments have emerged as a new and promising direction of research. In addition, to better simulate the stellar environment in the laboratory, research on nuclear physics under laser-driven plasma conditions has gradually become a frontier hotspot. In recent years, the CIAE team conducted a series of distinctive nuclear astrophysics studies, relying on the Jinping Underground Nuclear Astrophysics platform and accelerators in Earth’s surface laboratories, including the Beijing Radioactive Ion beam Facility, as well as other scientific platforms at home and abroad. This research covered nuclear theories, numerical models, direct measurements, indirect measurements, and other novel approaches, achieving great interdisciplinary research results, with high-level academic publications and significant international impacts. This article reviews the above research and predicts future developments.

The ¹²C+¹²C fusion reaction plays a crucial role in stellar evolution and explosions. Its main open reaction channels include , p, n, and ⁸Be. Despite more than a half century of efforts, large differences remain among the experimental data of this reaction measured using various techniques. In this work, we analyze the existing data using a statistical model. Our calculation shows the following: 1) the relative systematic uncertainties of the predicted branching ratios decrease as the predicted ratios increase; 2) the total modified astrophysical S-factors (S ^* factors) of the p and channels can be obtained by summing the S ^* factors of their corresponding ground-state transitions and the characteristic rays, while taking into account the contributions of the missing channels to the latter. After applying corrections based on branching ratios predicted by the statistical model, an agreement is achieved among the different data sets at E _cm> 4 MeV, while some discrepancies remain at lower energies, suggesting the need for better measurements in the near future. We find that theS ^* factor recently obtained from an indirect measurement is inconsistent with the direct measurement value at energies below 2.6 MeV. We recommend upper and lower limits for the ¹²C+¹²C S ^* factor based on the existing models. A new ¹²C+¹²C reaction rate is also recommended.

Recent determinations of the total rate of the ¹²C+¹²C nuclear reaction show non-negligible differences with the reference reaction rate commonly used in previous stellar simulations. In addition, the current uncertainties in determining each exit channel constitute one of the main uncertainties in shaping the inner structure of super asymptotic giant branch stars that could have a measurable impact on the properties of pulsating ultramassive white dwarfs (WDs). We explore how new determinations of the nuclear reaction rate and its branching ratios affect the evolution of WD progenitors. We show that the current uncertainties in the branching ratios constitute the main uncertainty factor in determining the inner composition of ultramassive WDs and their progenitors. We found that the use of extreme branching ratios leads to differences in the central abundances of ²⁰Ne of at most 17%, which are translated into differences of at most 1.3% and 0.8% in the cooling times and size of the crystallized core, respectively. However, the impact on the pulsation properties is small, less than 1 s for the asymptotic period spacing. We found that the carbon burns partially in the interior of ultramassive WD progenitors within a particular range of masses, leaving a hybrid CONe-core composition in their cores. The evolution of these new kinds of predicted objects differs substantially from the evolution of objects with pure CO cores. Differences in the size of the crystallized core and cooling times of up to 15% and 6%, respectively, lead to distinct patterns in the period spacing distribution.