Neutron Proton Pairing

In N=Z nuclei, neutrons and protons occupy the same orbitals. This gives rise to unusual effects. In even-even nuclei, there is a large binding energy anomaly (Wigner energy). In odd-odd nuclei, there are ground state 0⁺ and 1⁺ doublets. Energy differences between orbitals in different shells, as deduced from binding energies along the N=Z line, disagree substantially with spacing calculated using Woods -Saxon single-particle potentials.

We shall discuss these phenomena in the framework of a model that includes T=1 and T=0 n-p pairing in addition to the usual T=1 n-n and p-p pairing. By including four nucleon correlations explicitly in variational wave functions, we can explain these phenomena in a particularly simple way. We shall also discuss the excited state spectrum arising from the generalized pairing Hamiltonian as well as an extension of this approach to include deformation.

More information can be found in :

• the program
  

Marek Ploszajczak (GANIL)
Piet Van Isacker (GANIL)