Lifetimes in the yrast sequence of ${}_{}{}^{128}{}_{}{}^{}\mathrm{Ce}$ have been measured following the reaction ${}_{}{}^{92}{}_{}{}^{}\mathrm{Zr}$(${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$,4n) induced by 159-MeV ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$ ions. A Doppler-shift recoil-distance device was utilized inside a large NaI detector where the latter provided total $\gamma$-ray decay energy selection for these measurements. The $B\left(E2\right)$ values deduced for the $2^{+}$ through ${14}^{+}$ states indicate that in the ground band ${}_{}{}^{128}{}_{}{}^{}\mathrm{Ce}$ conforms much more closely to rigid-rotor behavior than do the heavier cerium isotopes, and that in the $s$ band the shape parameters remain in the collective sector $-60\mathrm{}°<\gamma <0\mathrm{}°$, as predicted by cranked self-consistent theory.

• Received 29 May 1984

DOI:https://doi.org/10.1103/PhysRevC.30.1532