The effect of the pairing interaction on the energies of isobar analogue resonances in 112-124Sb and isospin admixture in 100-124Sn isotopes

In the present study, the effect of the pairing interaction and the isovector correlation between nucleons on the properties of the isobar analogue resonances (IAR) in Sb112-124 isotopes and the isospin admixture in Sn100-124 isotopes is investigated within the framework of the proton-neutron quasi-particle random phase approximation (pnQRPA). The form of the interaction strength parameter is related to the shell-model potential by restoring the isotopic invariance of the nuclear part of the total Hamiltonian. In this respect, the isospin admixtures in the Sn100-124 isotopes are calculated, and the dependence of the differential cross section and the volume integral J(F) for the Sn(He-3,t)Sb reactions at E(He-3) = 200 MeV occurring by the excitation of IAR on mass number A is examined. Our results show that the calculated value for the isospin mixing in the Sn-100 isotope is in good agreement with Colo et al's estimates (4-5%), and the obtained values for the volume integral change within the error range of the value reported by Fujiwara et al (53 +/- 5 MeV fm(3)). Moreover, it is concluded that although the differential cross section of the isobar analogue resonance for the (He-3,t) reactions is not sensitive to pairing correlations between nucleons, a considerable effect on the isospin admixtures in N approximate to Z isotopes can be seen with the presence of these correlations.