Improved shell-model effective interaction calculations and their applications to light nuclei.

We calculate two-body effective interactions starting from a free nucleon-nucleon interaction and apply these interactions in shell-model calculations for no-core model spaces where all particles of the nucleus are active. The spurious center-of-mass motion is explicitly removed from the Hamiltonian. The role of the kinetic-energy operator is examined for ¹⁶O and ¹⁷O. Convergence properties of no-core model spaces are shown for ⁴He and ¹⁸O. The starting-energy dependence is removed by employing the effective Hamiltonian approach of Lee and Suzuki, and the results are applied to the deuteron. Different single-particle wavefunctions are applied to formfactor calculations for ¹⁷O in the extreme single-particle model and the results for high-momentum transfer are compared with the experimental data