${}^{163,164}$Dy nuclei have been measured by use of the Oslo method on data from pick-up ${(}^3\mathrm{He},\alpha )$ and inelastic scattering ${(}^3\mathrm{He}{,}^3{\mathrm{He}}^{\prime })$ reactions, respectively. The level densities for these dysprosium isotopes together with previously measured ${}^{160–162}$Dy are extracted in the region below the neutron binding energy. Thermodynamic properties are deduced within both micro-canonical and canonical ensemble theories. A phase transition from the pair-correlated state at low energies to a less correlated or uncorrelated state is studied in both ensembles. It is investigated whether the temperature of the nucleus is constant or a varying function of excitation energy. It is found that above an excitation energy of 3 MeV the temperature of all five dysprosium nuclei have a constant value within the experimental uncertainties. The impact of a constant-temperature level density versus a Fermi gas level density is discussed with respect to the canonical heat capacity.

• Received 1 March 2011

DOI:https://doi.org/10.1103/PhysRevC.85.014323