Empirical effective interactions in the lower fp shell and upper sd shell

Average values of matrix elements of the effective nucleon-nucleon interaction can be extracted from measured binding energies and spectra using a variety of simple techniques. Such techniques are applied to data in the mass range A=28--64 to yield information about the interaction energy of nucleons occupying the 2s1/2, 1d3/2, 1f7/2, and 2p3/2 shell-model orbits. The resulting interaction centroids are compared with values provided by other methods, such as shell-model fits to experimental energy levels, calculation of the G matrix from free nucleon-nucleon potentials, and extraction of interaction matrix elements directly from the spectra of nuclei with two nucleons relative to a closed shell. The empirical centroids are shown to be surprisingly accurate