The effective interaction between nucleons deduced from nuclear spectra

Two-body matrix elements of the residual nucleon-nucleon interaction are extracted from experimental data throughout the periodic table and are used to determine the ranges and well depths of various components of a local interaction. The $T=1$ even and odd components of the central interaction both definitely require two wells with different ranges; a shorter-range attractive well with a longer-range repulsive one. The need for a tensor interaction and a two-body spin-orbit interaction is also explored and their inclusion improves the fit slightly.