Levels in Ru-99 populated by the (3He, 2n gamma) reaction: Complete particle-core multiplets

The energy-level structure of /sup 99/Ru was studied using the /sup 98/Mo(/sup 3/He, 2n..gamma..)/sup 99/Ru reaction at a bombarding energy of 13 MeV, in an attempt to populate an extensive set of non-yrast states. The experiments included ..gamma..-ray excitation functions, ..gamma..-..gamma.. coincidence measurements, ..gamma..-ray angular distributions, and ..gamma..-ray linear polarization measurements. A large number of non-yrast states were observed, with angular momenta ranging from (1/2) to (17/2). The comparison of experimental energies and electromagnetic transition properties to the predictions of a particle-rotor model is presented. This interpretation suggests that several complete particle-core multiplets have been populated. The population of non-yrast states is attributable to the properties of the reaction rather than any details of the nuclear structure involved.