The phonon and quasiparticle structure of the low-lying states in ${}^{188,190,192}\mathrm{Os}$ is investigated within the microscopic quasiparticle-phonon model. An overall agreement with the data is obtained for energies and transitions. The properties of the $0^{+}$ states are found to be correlated with the evolution of the nuclear shape toward the $\gamma$-soft region. Special attention is devoted at the $4_3^{+}$ state. This state is found to be composed of a large double-$\gamma$ phonon component coexisting with an even larger one-phonon hexadecapole piece. Such a mixed phonon structure explains the observed, apparently contradictory, properties of the $4_3^{+}$ states in Os isotopes.

• Received 2 August 2008

DOI:https://doi.org/10.1103/PhysRevC.78.054304