  The structures, the electromagnetic transitions, and the beta decay strengths
of exotic nuclei are investigated within an extended cluster model. We start by
deriving an effective nuclear Hamiltonian within the $S_2$ correlation
operator. Tensor forces are introduced in a perturbative expansion which
includes up to the second order terms. Within this Hamiltonian we calculate the
distributions and the radii of A=3,~4 nuclei. For exotic nuclei characterized
by n valence protons/neutrons we excite the structure of the closed shell
nuclei via mixed modes formed by considering correlations operators of higher
order. Good results have been obtained for the calculated transitions and for
the beta decay transition probabilities.
