  The isospin breaking effects due to the Coulomb interaction in weakly-bound
nuclei are studied using the Gamow Shell Model, a complex-energy configuration
interaction approach which simultaneously takes into account many-body
correlations between valence nucleons and continuum effects. We investigate the
near-threshold behavior of one-nucleon spectroscopic factors and the structure
of wave functions along an isomultiplet. Illustrative calculations are carried
out for the T=1 isobaric triplet. By using a shell-model Hamiltonian consisting
of an isoscalar nuclear interaction and the Coulomb term, we demonstrate that
for weakly bound or unbound systems the structure of isobaric analog states
varies within the isotriplet and impacts the energy dependence of spectroscopic
factors. We discuss the partial dynamical isospin symmetry present in
isospin-stretched systems, in spite of the Coulomb interaction that gives rise
to large mirror symmetry breaking effects.
