Observation of Thermodynamical Properties in the ${}^{162}\mathrm{Dy}$, ${}^{166}\mathrm{Er}$, and ${}^{172}\mathrm{Yb}$ Nuclei

The density of accessible levels at low spin in the ( ${}^3\mathrm{He},\alpha \gamma$) reaction has been extracted for the ${}^{162}\mathrm{Dy}$, ${}^{166}\mathrm{Er}$, and ${}^{172}\mathrm{Yb}$ nuclei. The nuclear temperature is measured as a function of excitation energy in the region of 0–6 MeV. The temperature curves reveal structures indicating the onset of new degrees of freedom. The heat capacity of the nuclear system is discussed within the framework of a canonical ensemble.