Abstract
We study Fermi transitions and isospin mixing in an isotopic chain considering various approximations that use the same Skyrme-Hartree-Fock single-particle basis. We study Coulomb effects as well as the effect of BCS and quasiparticle random phase approximation (QRPA) correlations. A measure of isospin mixing in the approximate ground state is defined by means of the expectation value of the isospin operator squared in nuclei (which is generalized to nuclei). Starting from a strict Hartree-Fock approach without Coulomb interaction, it is shown that the isospin breaking is negligible, on the order of a few per thousand for , increasing to a few percent with Coulomb interaction. Pairing correlations induce rather large isospin mixing and Fermi transitions of the forbidden type for , and for . The enhancement produced by BCS correlations is compensated to a large extent by QRPA correlations induced by isospin-conserving residual interactions that tend to restore isospin symmetry.
- Received 29 November 2004
DOI:https://doi.org/10.1103/PhysRevC.71.044308
©2005 American Physical Society