A very unusual rotational band has been found in ${}_{}{}^{178}{}_{}{}^{}\mathrm{Os}$. It consists of seven regularly spaced transitions about 36 keV apart, which correspond closely to that of the superdeformed band in ${}_{}{}^{152}{}_{}{}^{}\mathrm{Dy}$ after an $A^{\frac{5}{3}}$ normalization. This band populates the yrast band directly, thus permitting rather reliable spin assignments. Based on these, the moment of inertia $J^{\mathrm{}\left(1\right)\mathrm{}}$ is found to be much smaller than the $J^{\mathrm{}\left(2\right)\mathrm{}}$ derived from the above $\gamma$-ray spacings. The most likely interpretation of this is a band with large deformation which is undergoing systematic changes in deformation, pairing, and/or alignment.

• Received 25 July 1988

DOI:https://doi.org/10.1103/PhysRevC.38.2470