Two-body matrix elements from a modified surface delta interaction

The addition of a T-dependent but J-independent term to the surface delta interaction greatly improves the agreement between the values of the two-body matrix elements calculated from this interaction and the corresponding values obtained both from emperical fits to level energies and from a realistic (Hamada-Johnston) interaction. This is shown for 1d-2s and 1f-2p configurations. The use of this modified surface delta interaction as a shell-model residual interaction produces good agreement between the calculated and experimental energies ofmany-nucleon configurations. In particular, total binding energies and the energy spacings between levels of different isospin are fitted much better than is possible without the use of the extra T-dependent term