This work is concerned with the use of different "effective" nucleon-nucleon interactions in the calculation of binding energies and spectra of some of the oxygen isotopes. The variational procedure consists of using a complete set of Slater determinant wave functions, having the same total M value for the projection of the angular momentum, in order to minimize the ground states of various nucleonic configurations in.the 2s-ld nuclei. The parameters obtained are used'in the subsequent diagonalization of the Hamiltonian and its eigenvalues are interpreted as energy eigenvalues. The calculations performed in this work led to the conclusion that the density dependence of the effective force is extremely important and should not be neglected, at least in the calculation of binding energies. / Thesis / Master of Science (MS)