I suggest that the anomaly at I${=6\mathrm{}}^{+}$ in the ground-state band of ${}_{}{}^{172}{}_{}{}^{}\mathrm{Os}$ results from the increase from two to three in the difference in nucleon number of the revolving cluster when I increases to I+2, and that the yrast cusp at I${=16\mathrm{}}^{+}$ corresponds to the change in structure from one revolving cluster to two revolving clusters. Values of the electric quadrupole moment are predicted.

• Received 24 August 1987

DOI:https://doi.org/10.1103/PhysRevC.37.883