The shape transition in the neutron-rich Os isotopes is studied by investigating the neutron-rich ${}^{196}\text{Os}$ nucleus through in-beam $\gamma$-ray spectroscopy using a two-proton transfer reaction from a ${}^{198}\text{Pt}$ target to a ${}^{82}\text{Se}$ beam. The beam-like recoils were detected and identified with the large-acceptance magnetic spectrometer PRISMA, and the coincident $\gamma$ rays were measured with the advanced gamma tracking array (AGATA) demonstrator. The de-excitation of the low-lying levels of the yrast-band of ${}^{196}\text{Os}$ were identified for the first time. The results are compared with state-of-the-art beyond-mean-field calculations, performed for the even-even ${}^{188-198}\mathrm{Os}$ isotopes. The new results suggest a smooth transition in the Os isotopes from a more axial rotational behavior towards predominately vibrational nuclei through triaxial configurations. An almost perfect $\gamma$-unstable/triaxial rotor yrast band is predicted for ${}^{196}\text{Os}$ which is in agreement with the experimentally measured excited states.

• Received 14 July 2014

DOI:https://doi.org/10.1103/PhysRevC.90.021301