Microscopic study of the 7Li(n,γ)8Li and 7Be(p,γ)8B reactions in a multiconfiguration three-cluster model

The three-cluster generator coordinate method is applied to the 7Li(n,γ)8Li and 7Be(p,γ)8B capture reactions. The 8B (or 8Li) nucleus is defined by a mixing of (α+3He)+p and (α+p)+3He (or mirror) configurations. We investigate the sensitivity of different observables with respect to the nucleon-nucleon interaction by considering four different Volkov forces. For all of them, the model fairly reproduces most of the experimentally known spectroscopic properties of the 8B and 8Li mirror nuclei. Recent measurements of the quadrupole moments are well explained without a halo structure. The 7Li(n,γ)8Li cross section supports the data of Imhof et al. rather than those of Wiescher et al. At zero energy, the 7Be(p,γ)8B astrophysical S-factors slightly depend on the nucleon-nucleon interaction. They are consistent with the currently accepted value, but contradict lower estimates. (orig.)