Theoretical Resonance Calculations for the Isobaric Analogs 133Sn and 133Sb

Nicolae Istrate


The formation of a compound nucleus during a nuclear reaction is identified by resonances in the excitation function. Isobaric analog resonances are a special type of resonance that have a narrow width and denote a pair of isobars. Isobaric analog resonances are caused by the isospin correlation between isobaric analog states. The isospin correlation is a direct result of the mechanism of (p, n) nuclear reactions. By analyzing isobaric analog resonances, valuable information about unstable exotic nuclei can be determined. This technique has become a standard in the repertoire of the experimental nuclear physicist. A theoretical calculation of isobaric analog resonances corresponding to elastic proton scattering off 132Sn is performed in the energy range 5.0 to 15.0 MeV. By analyzing the excited states of the compound nucleus 133Sb, the single particle states of its isobar 133Sn are predicted. A total of five energy levels of 133Sn are identified for the 7.5 to 9.5 MeV center of mass energy range. An additional resonance with spin-parity JΠ = 5/2+ is identified in the energy range 12.0 to 13.5 MeV and corresponds to an unusual phase shift. The exact characteristics of this resonance could not be determined, although the shape of the excitation function suggests an isobaric analog resonance which would correspond to an unidentified energy level of 133Sn.