The excitation spectra of nuclei in the regions $150<A<190$ and $220<A<250$ are commonly considered as showing characteristics of the rotational motion. In the present work, however, there is evidence indicating that the nuclei can evolve from rotation to vibration. We have used two simple models to discuss the collective motions of a nucleus for different spin ranges. In addition, in order to get the insight into the rotational-like properties of nuclei, as an example, shape calculations using the total Routhian surfaces (TRS) model have been carried out for positive-parity states in ${}^{156}\mathrm{Gd}$. Also we have shown the result of the nucleus ${}^{102}\mathrm{Ru}$ which is given as an example of the reverse transition, i.e., vibration to rotation. The TRS plots reveal that, with increasing spin, the former nucleus becomes slightly soft in $\gamma$ and $\beta$ deformations, while the latter one becomes rigid in the $\gamma$ deformation.

• Received 23 October 2006

DOI:https://doi.org/10.1103/PhysRevC.75.047304