  The He3(He4,gamma)Be7 and H3(He4,gamma)Li7 reactions are studied in an
extended two-cluster model which contains alpha+h/t and Li6+p/n
clusterizations. We show that the inclusion of the Li6+p/n channels can
significantly change the zero-energy reaction cross sections, S(0), and other
properties of the Be7 and Li7 nuclei, like the quadrupole moments Q. However,
the results agree with the known correlation trend between S(0) and Q.
Moreover, we demonstrate that the value of the zero-energy derivatives of the
astrophysical S-factors are more uncertain than currently believed.
