Superdeformed bands observed in ${}^{131}$Ce, ${}^{132}$Ce, and ${}^{133}$Ce have sequences of γ-ray transition energies that exhibit a $\Delta I=2\mathrm{}$ staggering. This staggering has different characteristics to that seen in previously known cases in other mass regions. The energy staggering starts at low rotational frequency ( $ħ\omega =3\mathrm{}$ MeV for ${}^{131}$Ce) at a magnitude of $\sim \pm 0.3$ keV, dies away to zero at intermediate frequency ( $ħ\omega =0.6-0.7\mathrm{}$ MeV), and reappears at higher frequencies ( $ħ\omega \sim 0.7$ MeV).

• Received 8 November 1995

DOI:https://doi.org/10.1103/PhysRevLett.76.3671