Full-symmetry and mixed-symmetry states in even ruthenium isotopes

The experimental data on positive parity, low-lying levels of the even ruthenium isotopes ${}_{}{}^{98-114}{}_{}{}^{}\mathrm{Ru}$ have been analyzed in the framework of the IBA-2 model, with the aim of identifying states having a large mixed-symmetry component. Energies, static and transition electric quadrupole and magnetic dipole moments as well as mixing and branching ratios of the relevant levels have been considered. It appears that the properties of all low-lying levels in these isotopes, for which the comparison between experiment and theory is possible, can be satisfactorily described by the standard IBA-2 model, provided proper account is taken of the presence at low energy of states having a mixed-symmetry character. It seems possible to identify, in each isotope, a few states having such a character, the lowest ones being the $2_3^{+}$ and $3_1^{+}$ levels. Some indications for the presence above the $3_1^{+}$ level of a band of states having $J^{\pi }=5_1^{+}, 7_1^{+}, 9_1^{+}$ and a comparable degree of mixed symmetry are pointed out for the heavier nuclei of the chain.