The E1 and E2 capture amplitudes in ¹²C(α,γ₀)¹⁶O

Abstract.

Excitation functions of the γ₀ capture transition in ¹²C(α,γ)¹⁶O at θ_γ= 90^˚ were obtained using a 4 × 4'' BGO crystal in close geometry (E= 0.94 to 3.39 MeV) and a 2 × 2'' BGO crystal in far geometry (E= 1.69 to 3.29 MeV), where the study of the reaction was initiated in inverse kinematics involving a windowless gas target. The small crystal detected essentially the E1 multipole component in the γ₀ capture transition, while the large crystal observed approximately the angle-integrated sum of the E1 and E2 multipole components. Analysis of the two data sets together with data from previous work provided strong evidence that both multipoles are of equal importance at the relevant stellar energy E ₀= 0.3 MeV.