The giant dipole resonance in 55Co

Recent measurements of the ⁵⁴Fe(p, γ)⁵⁵Co cross section indicate the existence of a splitting between the T_< and T_> components of the giant dipole resonance. We have calculated the (p, γ) cross section in the shell-model formalism. The bound-state interaction was determined by a fit to fp and sd shell nuclei. The calculation predicts the isospin splitting of ≈ 2.4 MeV and is consistent with all data in the energy region E_p = 9–15 MeV as well as the low-lying ⁵⁵Co spectrum.