Large scale shell-model calculations with an effective interaction derived from the realistic $G$-matrices were performed for $N=80$ isotones for which so-called mixed-symmetry states were recently observed experimentally. Calculated spectra are shown to be in good agreement with data. The calculated transition rates reveal the necessity of modifying the strength of the pairing interaction. The structure of mixed-symmetry $2^{+}$ states is analyzed in terms of seniority components and by decomposition into the $Q$-phonon scheme.

• Received 4 October 2009

DOI:https://doi.org/10.1103/PhysRevC.80.054311