PHYSICAL REVIEW C, cilt.74, sa.2, 2006 (SCI-Expanded)
The rare earth nuclei from N=92 to N=108 display a very regular pattern of empirically extracted interactions of the last protons with the last neutrons. The simplicity of the empirical systematics suggests that a simple interpretation should be possible. We discuss calculations of these proton-neutron (p-n) interactions with a zero-range delta force.