Quadrupole Strength in Isobaric Triplets

The dependence of the $E2$ matrix elements on isospin projection Tz is linked to the conservation of the isospin symmetry. To study this conjecture, we calculated the B(E2: 2⁺ → 0⁺) rates for the even-even $T=1$ mirror nuclei with $42$ ≤ A ≤ $98$ within nuclear density functional theory, employing the generalized Bohr Hamiltonian, and carrying out angular momentum projection. We demonstrated that collective effects are crucial for describing experimental data near the $N=Z$ line without invoking explicit beyond-Coulomb isospin symmetry-breaking corrections. We also determined the B(E2↓) values for odd-odd Tz=0 nuclei ⁷⁰Br and ⁷⁸Y in doubly-blocked configurations. We discussed the requirements for accurately describing isobaric analog states and emphasized how current theoretical results should be interpreted within the study of isospin symmetry across isospin triplets.