Illustration: Carin Cain

Figure 2: Schematic illustration of the sign of the monopole interaction arising from the tensor force for nucleons in different orbits. The grey area indicates schematically that this is the average monopole interaction and that it is the orientations of the spins relative to the orbital angular momentum (the large ribbon arrows) that matter. The $>$ and $<$ subscripts indicate whether the spin of the nucleon is parallel or antiparallel to its orbital angular momentum. The attractive or repulsive nature of this interaction is evident in the effective force between valence nucleons, as well as in the mean field for all unoccupied orbits.