Indirect study of the ⁷Be(α,γ)¹¹C reaction

The chemical evolution of Carbon-12 in nature is of great interest due to the importance of this element in the formation of organic compounds. The production of carbon-12 occurs naturally in low metallicity stars through the so-called Hot P-P chain. This process is described by the chain ⁷Be(α, γ)¹¹C(p, γ)¹²N(β,v)¹²C. However, the reaction rates for this process remain uncertain. In particular, the first reaction of the chain has significant uncertainties at the lowest energies due to the presence of the subthreshold resonance in ¹¹C (3/2⁺ state at 7.5 MeV) which dominates the α-capture at energies below a few hundred keV. One way to constrain this reaction rate is to apply an indirect method and populate the subthreshold state in ¹¹C using the ⁷Be(⁶Li, d)¹¹C α-transfer reaction. We developed a new high-efficiency experimental setup that allows low-energy measurements of the α-transfer reactions to sub-threshold states. This is done using an efficient γ array and a silicon detector placed at zero degrees on the beam axis after the ⁶Li which is thick enough to absorb the ⁷Be beam, but still thin enough to allow for transmission of deuteron recoils. Deuterons are measured in coincidence with the γ-rays (7.5 MeV in this case). The cross-section for the α-transfer reaction measured this way will then be used to determine the α-asymptotic normalization coefficient of the 3/2⁺ state at 7.5 MeV in ¹¹C, constraining the ⁷Be(⁶Li, d)¹¹C reaction cross section at the lowest energies. The presented project discusses the Monte Carlo simulations being developed to study the feasibility of the proposed technique.