Particle-hole symmetry, F-spin, and r-process parameters

We exploit approximate symmetry under particle-hole conjugation and the systematics associated with a classification scheme (inspired by the neutron-proton interacting boson model) to obtain estimates of binding energies and low-lying excitation energies for even-even r-process nuclei drawn from the major proton and neutron shells, 50<Z<82 and 82<N<126. We anticipate that our simple formalism for binding energies, depending on only six parameters, has an accuracy of 0.8 MeV. We argue that the particular dual particle-hole conjugation symmetry required to relate excitation energies in neutron-rich nuclei to the known excitation energies of the corresponding conjugated nuclei holds to within 10% or so.