Constraints on the ⁷Be(p,γ)⁸B radiative capture rate from charge symmetry

Cross sections for the dipole radiative capture reactions ⁷Li(n,γ)⁸Li and ⁷Be(p,γ)⁸B are calculated in a two-body model, which is based on a Woods-Saxon parametrization of the nuclear interaction. The well depth is adjusted for each reaction channel so that the measured separation energies and s-wave scattering lengths are reproduced. The calculations are repeated for a wide range of the radius and the diffuseness of the interaction. The predicted S factor for the radiative proton capture on ⁷Be falls within a surprisingly narrow range of values when the model is calibrated to reproduce measurements of the mirror reaction ⁷Li(n,γ)⁸Li. The simplified model used here is consistent with the shell model approach for proton capture on ⁷Be but it gives a significantly smaller cross section for neutron capture on ⁷Li.