The need for long range components in the effective nuclear interaction

It is shown that if one uses single particle energies from experiment and a delta residual interaction it is not possible to obtain the energy of the giant dipole and spurious states of ²⁰⁸Pb, and at the same time obtain reasonable results for the low lying two-particle spectra of ²¹⁰Pb or ²¹⁰Po. Related to the above problem, the isobaric analog state of ²⁰⁸Pb (in ²⁰⁸Bi) comes much too low in calculations using realistic interactions. It is noted here that the above difficulties can be overcome, phenomenologically at least, by adding to the effective interaction some long range repulsive components. The Bansal-French and the Schiffer interactions are examples of these. However, the dipole-dipole component of the Schiffer interaction gives much too large a splitting between the dipole state and spurious state.