Odd Co Isotopes in a Unified Vibrational Model

The odd-$A$ Co isotopes are studied in a version of the unified vibrational model which incorporates both anharmonic and quasiparticle effects. With the $p_{\frac{1}{2}}$, $p_{\frac{3}{2}}$, $f_{\frac{5}{2}}$, and $f_{\frac{7}{2}}$ orbitals available, quasihole states are coupled to anharmonic vibrations of the corresponding Ni cores. Very good agreement is obtained with the known properties of ${}_{}{}^{57-59}{}_{}{}^{}\mathrm{Co}$ in a one-parameter fit, while the ${}_{}{}^{61-63}{}_{}{}^{}\mathrm{Co}$ calculations are essentially parameter free. The systematics of the energy levels of ${}_{}{}^{57-63}{}_{}{}^{}\mathrm{Co}$ can also be explained well by the model.