The level structures of several Ru isotopes near $A=104\mathrm{}$ have been studied in the fission of the compound nucleus ${}^{197}\mathrm{Pb},$ formed in the ${}^{24}{\mathrm{Mg}\mathrm{}+}^{173}\mathrm{}\mathrm{Yb}$ reaction at 134.5 MeV. A sequence of five transitions, observed in coincidence with known transitions in the ${}^{86}\mathrm{Sr}$ and ${}^{87}\mathrm{Sr}$ complementary fragments, has been assigned to ${}^{105}\mathrm{Ru}.\mathrm{}$ Comparison with the neighboring odd-mass Ru isotopes supports assignment of this sequence as built on the $h_{11/2}$ excitation in ${}^{105}\mathrm{Ru}.$ The positive-parity band built on the ${7/2}^{+}$ state of ${}^{103}\mathrm{Ru}$ has been extended above the backbending induced by the alignment of two $h_{11/2}$ neutrons. In addition, the ground-state bands of ${}^{104}\mathrm{Ru}$ and ${}^{106}\mathrm{Ru}$ have been extended to higher spins.

• Received 28 April 1998

DOI:https://doi.org/10.1103/PhysRevC.58.1997