  We present a study of the effects of the tensor-isospin term of the effective
interaction in Hartree-Fock and Random Phase Approximation calculations. We
used finite-range forces of Gogny type, and we added to them a tensor-isospin
term which behaves, at large internucleonic distances, as the analogous term of
the microscopic interactions. The strength of this tensor force has been chosen
to reproduce the experimental energy of the lowest 0$^-$ excited state in
$^{16}$O, which shows large sensitivity to this term of the interaction. With
these finite-range interactions, we have studied the effects of the
tensor-isospin force in ground and excited states of carbon, oxygen, calcium,
nickel, zirconium, tin and lead isotopes. Our results show that the tensor
force affects mainly the nucleon single particle energies. However, we found
some interesting cases where also bulk nuclear properties are sensitive to the
tensor interaction.
