New local mass relation for isobaric analogue states and isospin-nonconserving forces

In this paper a new local mass relation is constructed for isobaric analogue states of four relating neighboring nuclei. The standard deviation from a linear fit of experimental data is 20-70 keV. The systematics of the local mass relation is discussed in terms of an empirical Coulomb energy formula and the isobaric multiplet mass equation. The local relation for nuclei in the pf shell is studied in the framework of the microscopic shell model. The results demonstrate the key roles played by the Coulomb interaction and an effective isospin-nonconserving nucleon-nucleon interaction in our new mass relation.