The E1 capture amplitude in 12C(α, γ0)16O

An excitation function of the ground-state γ0-ray capture transition in 12C(α, γ)16O at θγ = 90° was obtained in far geometry using six Ge detectors, where the study of the reaction was initiated in inverse kinematics involving a windowless gas target. The detectors observed predominantly the E1 capture amplitude. The data at E = 1.32 to 2.99 MeV lead to an extrapolated astrophysical S factor SE1(E0) = 90 ± 15 keV b at E0 = 0.3 MeV (for the case of constructive interference between the two lowest E1 sources), in good agreement with previous works. However, a novel Monte Carlo approach in the data extrapolation reveals systematic differences between the various data sets such that a combined analysis of all available data sets could produce a biased estimate of the SE1(E0) value. As a consequence, the case of destructive interference between the two lowest E1 sources with SE1(E0) = 8 ± 3 keV b cannot be ruled out rigorously.