Consistent cluster model description of the electromagnetic properties of lithium and beryllium nuclei

We calculate the electromagnetic properties of lithium and beryllium nuclei with a resonating group model using bare charges and g-factors. For 6Li we give results for reduced transition strengths and explain the tiny quadrupole moment. For 7Li and 7Be we compute electromagnetic moments and transitions between bound states. Furthermore we reproduce the existing data on the radiative captures 3He(α,γ)7Be and 3H(α,γ)7Li. In the 7Li case the calculations indicate an increase of the astrophysical S-factor for decreasing energy which might have astrophysical consequences. We show that closed channels do not influence results on the astrophysical S-factor at low energy. Finally we demonstrate that the polarisability of 7Li originates from the virtual break-up at low energies. In this case, the 6Li+n channels contribute appreciably. (orig.)