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.

The ${}^{12}\mathrm{C}(\alpha ,\gamma ){}^{16}\mathrm{O}$ reaction is one of the most crucial reactions in nuclear astrophysics. The $E2$ external capture to the ${}^{16}\mathrm{O}$ ground state (GS) has not been emphasized in previous analyses but may make a significant contribution to the ${}^{12}\mathrm{C}(\alpha ,\gamma ){}^{16}\mathrm{O}$ cross section depending on the value of the GS asymptotic normalization coefficient (ANC). In the present work, we determine this ANC to be $337\pm 45{\mathrm{fm}}^{-1/2}$ through the ${}^{12}\mathrm{C}({}^{11}\mathrm{B},{}^7\mathrm{Li}){}^{16}\mathrm{O}$ reaction using a high-precision magnetic spectrograph. This sheds light on the existing large discrepancy of more than 2 orders of magnitude between the previously reported ANC values. Based on the new ANC, we experimentally constrain the GS external capture and show that through interference with the high energy tail of the $2^{+}$ subthreshold state, a substantial enhancement in the GS $S_{E2}(300)$ factor can be obtained ($70\pm 7\mathrm{keV}\mathrm{b}$) compared to that of a recent review (45 keV b), resulting in an increase of the total $S$ factor from 140 to 162 keV b, which is now in good agreement with the value obtained by reproducing supernova nucleosynthesis calculations with the solar-system abundances. This work emphasizes that the external capture contribution for the ground state transition cannot be neglected in future analyses of the ${}^{12}\mathrm{C}(\alpha ,\gamma ){}^{16}\mathrm{O}$ reaction.

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.

${}^{26}\mathrm{Al}$ with a half-life of $7.17\times {10}^5$ years is one of the most significant nuclides in $\gamma$-ray astronomy and presolar grains of meteorites. Its main production mechanism in the $\mathrm{H}$-burning MgAl cycle is the ${}^{25}\mathrm{Mg}(p,\gamma ){}^{26}\mathrm{Al}$ reaction. In the temperature region of 0.05–0.3 GK of astrophysical interest, the astrophysical ${}^{25}\mathrm{Mg}(p,\gamma ){}^{26}\mathrm{Al}$ reaction rate is dominated by the resonant capture of several low-energy resonances. In this work, we report the results of a complete experimental investigation of the $E_{\mathrm{c}.\mathrm{m}.}=92$, 130, and 189 keV resonances in the ${}^{25}\mathrm{Mg}(p,\gamma ){}^{26}\mathrm{Al}$ reaction with the Jinping Underground Nuclear Astrophysics Experimental Facility. The updated thermonuclear ${}^{25}\mathrm{Mg}(p,\gamma ){}^{26}\mathrm{Al}$ reaction rate is (32–39)% higher than that obtained at the Laboratory for Underground Nuclear Astrophysics around 0.07–0.09 GK, mainly due to the 32% enhancement of the 92-keV resonance strength. The astrophysical impact of our new rate on the ${}^{26}\mathrm{Al}$ yield in a 5 ${\mathrm{M}}_{\odot }$ low-metallicity asymptotic giant branch star is investigated, in which an increase of (45–79)% in the ${}^{26}\mathrm{Al}$ yield is found by adopting our new ${}^{25}\mathrm{Mg}(p,\gamma ){}^{26}\mathrm{Al}$ rates.