First experimental constraint of the spectroscopic amplitudes for the α-cluster in the 11B ground state

We present the first experimental determination on the spectroscopic amplitudes (SAs) for the α-cluster in the B11 ground state via the Li7(Li6,d)11B reaction using a high-precision magnetic spectrograph. This is believed to have a strong effect on the studies of α-induced reactions which are crucial in nuclear astrophysics. It is found that the previous SAs of B11 from shell model calculations cause overestimations of up to 23% for the C12(α,γ)16O SE2(300) factor and up to 34% for the C13(α,n)16O S(190) factor with respect to the results from the present experimentally determined SAs. Due to the importance of these two reactions, for example the uncertainty in the C12(α,γ)16O cross section at Ec.m. = 300 keV is required to be better than 10% by stellar modeling, the new S-factors could result in a potential influence on the astrophysical network calculations.