12C(α,γ)16O是恒星氦燃烧中最关键的核反应之一，它影响碳以上的元素合成和大质量恒星的演化及命运。尽管国际上已通过各种实验方法对该反应开展了广泛测量，但反应率的精度仅达到~40%，未能满足恒星演化模型对其精度的要求（<10%）。影响12C(α,γ)16O反应率精度的最大因素是7.117 MeV 1- 和6.917 MeV 2+的两个阈下共振。 本项目将采用截面较大的转移反应替代天体低能区截面极小的(α,γ)反应的研究思路。使用串列加速器和高精度磁谱仪，精确测量α集团转移反应12C(11B,7Li)16O布居16O的7.117 MeV 1- 和6.917 MeV 2+两个阈下共振态的角分布，进而确定12C(α,γ)16O反应中两条阈下共振的约化α宽度，研究并理解原先(6Li,d)和(7Li,t)给出的结果间4-5倍的分歧，最终给出12C(α,γ)16O反应的天体物理S因子和反应率。

12C(α,γ)16O is one of the key reactions in stellar He-burning, which affects the synthesis of the elements heavier than carbon and affects the evolution and fate of massive stars. Although this reaction has been extensively investigated via many experimental methods, the precision of its rate only reached about 40% significantly larger than that (<10%) required by the model of stellar evolution. The most important contributions to the 12C(α,γ)16O reaction rate are two subthreshold resonances via the 7.117 MeV 1? and 6.917 MeV 2+ levels in 16O. This project will study the 12C(α,γ)16O reaction with very small cross sections at low energies of astrophysical relevance by using the transfer reaction with larger cross sections. The angular distribution of the 12C(11B,7Li)16O reaction leading to the 7.117 MeV 1? and 6.917 MeV 2+ levels in 16O will be measured using tandem accelerator and high-precision magnetic spectrograph, and then used to determine the reduced α-width of two subthreshold resonances to understand the discrepancy of up to a factor of 4-5 in the preexisting results. The astrophysical S-factors and rate of the 12C(α,γ)16O reaction will be derived finally.