The neutron-proton interaction energy of the valence nucleons

Summary

The fermion-fermion, fermion-boson and boson-boson neutron-proton interaction energies of valence nucleons and dinucleons, ε_{p l −n j} , ε_{p l −2n j} , ε_{n j −2p j} , and ε_{2p l −2n j} , are calculated for a great number of 1f _7/2 nuclei. These energies are almost unchanged if every neutron is converted into a proton and vice versa, and are extremely dependent on therank of the partners in the shells, being maximum when the partners have the same rank. A strong enhancement of the various neutron-proton interactions is observed at shell closure and confirms that spin-orbit effects and neutron-proton interaction are closely related. The diproton-dineutron interaction is shown to follow laws similar to those of the fermionic n-p interaction. The extremely energy-rich interaction between diprotons and dineutrons of rank 1 observed in the⁴He valence shells and even in the 1d _5/2 shell is still observed in the 1f _7/2 shells. Another anomaly, the enhanced n₂-p₂ interaction energy, observed in the⁴He valence shells but not in the 1d _5/2 shells, is observed in the 1f _7/2 shells. Recognition of the existence of these anomalies in the⁴He shells leads to a better understanding of the properties of these valence shells than in a previous approach. Knowledge of the «from core» detachment energies and of the various neutron-proton interaction energies allows a visualization of the energetic structure of many 1f _7/2 nuclei in their ground state.