FULL-SYMMETRY AND MIXED-SYMMETRY STATES IN EVEN RUTHENIUM ISOTOPES

The experimental data on positive parity, low-lying levels of the even ruthenium isotopes Ru-98-114 have been analyzed in the framework of t he IBA-2 model, with the aim of identifying states having a large mixe d-symmetry component. Energies, static and transition electric quadrup ole and magnetic dipole moments as well as mixing and branching ratios of the relevant levels have been considered. It appears that the prop erties of all low-lying levels in these isotopes, for which the compar ison between experiment and theory is possible, can be satisfactorily described by the standard IBA-2 model, provided proper account is take n of the presence at low energy of states having a mixed-symmetry char acter. It seems possible to identify, in each isotope, a few states ha ving such a character, the lowest ones being the 2(3)(+) and 3(1)(+) l evels. 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 d egree of mixed symmetry are pointed out for the heavier nuclei of the chain.