Isospin mixing and the sum rule of super-allowed fermi β decay

The amplitudes of isospin mixing to the ground states of 14O and several odd-odd N  Z nuclei are studied in the Hartree-Fock approximation taking into account charge symmetry and charge independence breaking forces. We find that isospin mixing increases the sum rule of super-allowed Fermi transitions by 0.1 % in 14O and by more than 1 % in 54Co because of core effects, while valence particles tend to decrease the sum rule. It is shown that the sum rule increases due to the CSB and CIB interactions amounts to about 40% of that due to the Coulomb interaction alone.