Аннотация:Background: The 12C(α, γ )16O reaction, determining the survival of carbon in red giants, is of interest fornuclear reaction theory and nuclear astrophysics. A specific feature of the 16O nuclear structure is the presence oftwo subthreshold bound states, (6.92 MeV, 2+) and (7.12 MeV, 1−), that dominate the behavior of the low-energyS factor. The strength of these subthreshold states is determined by their asymptotic normalization coefficients(ANCs), which need to be known with high accuracy.Purpose: The objective of this research is to examine how the subthreshold and ground-state ANCs impact thelow-energy S factor, especially at the key astrophysical energy of 300 keV.Method: The S factors are calculated within the framework of the R-matrix method using the AZURE2 code.Results: Our total S factor takes into account the E1 and E2 transitions to the ground state of 16O includingthe interference of the subthreshold and higher resonances, which also interfere with the corresponding directcaptures, and cascade radiative captures to the ground state of 16O through four subthreshold states: 0+2 , 3−, 2+,and 1−. To evaluate the impact of subthreshold ANCs on the low-energy S factor, we employ two sets ofthe ANCs. The first selection, which offers higher ANC values, is attained through the extrapolation process[Blokhintsev et al., Eur. Phys. J. A 59, 162 (2023)]. The set with low ANC values was employed by deBoer et al.[Rev. Mod. Phys. 89, 035007 (2017)]. A detailed comparison of the S factors at the most effective astrophysicalenergy of 300 keV is provided, along with an investigation into how the ground-state ANC affects this S factor.Conclusion: The contribution to the total E1 and E2 S factors from the corresponding subthreshold resonancesat 300 keV are (71–74)% and (102–103)%, respectively. The correlation of the uncertainties of the subthresholdANCs with the E1 and E2 S(300 keV) factors is found. The E1 transition of the subthreshold resonance 1−does not depend on the ground-state ANC but interferes constructively with a broad (9.585 MeV; 1−) resonancegiving (for the present subthreshold ANC) an additional 26% contribution to the total E1 S(300 keV) factor.Interference of the E2 transition through the subthreshold resonance 2+ with direct capture is almost negligiblefor small ground-state ANC of 58 fm−1/2. However, its interference with direct capture for higher ground-stateANC of 337 fm−1/2 is significant and destructive, contributing −27%. The low-energy SE2 (300 keV) factorexperiences a smaller increase when both subthfreshold and the ground-state ANCs rise together due to theiranticorrelation, compared to when only the subthreshold ANCs increase.
