Exploring isospin asymmetry and independence along the N=Z line

The study of differences in excitation energy between analogue states in isobaric
multiplets allows to verify the validity of isospin symmetry and independence as a
function of the angular momentum. These differences are of the order of tens of keV
and can be well reproduced by state-of-the-art shell model calculations. Several
nuclear structure properties can be deduced from these data, such as the alignment
of nucleons along rotational bands, the evolution of the nuclear radius and the
identification of pure single particle excitations across two main shells. In addition,
the isospin breaking of the nuclear interaction is suggested by the systematic
comparison with data.
In the last years these studies have been extended from the nuclei in the f7/2 shell to
other mass regions due to the progress in the experimental techniques and the use of
radioactive beams. From the theoretical side the research of the origin of the isospin
breaking interaction is exploring different scenarios.
In this seminar, a systematic analysis of Coulomb energy differences is performed for
nuclei in the range A=20-60. A schematic, general method to calculate these energy differences
among analogue states will be presented that reproduces with very good accuracy the available data.
These results put in evidence the need of considering a charge-dependent nucleon-nucleon interaction.