High spin states in the $N=79\mathrm{}$ ${}^{137}\mathrm{Ce}$ nucleus have been studied with the reaction ${}^{124}\mathrm{Sn}{(}^{18}\mathrm{O}{,5n)}^{137}\mathrm{Ce}$ at beam energy 78 MeV. The level scheme has been expanded with spin up to $\frac{43}{2}ħ.$ At low spins, the yrast collective structure built on the $\nu h_{11/2}^{-1}\times 2^{+}$ multiplet shows a transitional shape with $\gamma =30.8\mathrm{}°$ according to calculations of the triaxial rotor-plus-particle model. The configurations for several high spin states have been discussed from a systematical comparison with neighboring nuclei. A collective band built on $I=33/2\mathrm{}$ level has been observed for the first time. This band has an oblate shape with $\gamma =-60°$ and most probably originates from the five-quasiparticle $\nu s_{1/2}\otimes [\nu h_{11/2}{]}^2\otimes \pi g_{7/2}\otimes \pi h_{11/2}$ configuration.

• Received 3 May 2000

DOI:https://doi.org/10.1103/PhysRevC.62.044310