High spin states in ${}^{178}\mathrm{Ir}$ were investigated by means of in-beam $\gamma$-ray spectroscopy techniques using the multidetector array GASP. Excited states of ${}^{178}\mathrm{Ir}$ were populated through the ${}^{159}\mathrm{Tb}{(}^{24}\mathrm{Mg},5n)$ fusion-evaporation reaction at ${E(}^{24}\mathrm{Mg})=131\mathrm{}–141$ MeV. Fourteen rotational bands have been observed and their configurations discussed. Alignments, band crossing frequencies, dynamical and kinematical moments of inertia, and electromagnetic properties have been analyzed in the framework of the cranking model. Signature inversion in the $\pi i_{13/2}\otimes \nu i_{13/2}$ and $\pi h_{9/2}\otimes \nu i_{13/2}$ structures has been identified and interpreted in the framework of the particle rotor model with residual $p-n$ interaction and variational moment of inertia. In bands involving the $\pi i_{13/2}$ orbital an increase in the deformation, relative to the other bands, has been found.

• Received 11 November 2002

DOI:https://doi.org/10.1103/PhysRevC.67.024308