Abstract
The nuclear level densities of and below the neutron separation energy have been measured using transfer and scattering reactions. All the level density distributions follow the constant-temperature description. Each group of isotopes is characterized by the same temperature above the energy threshold corresponding to the breaking of the first Cooper pair. A constant entropy excess and is observed in and with respect to and , respectively, giving information on the available single-particle level space for the last unpaired valence neutron. The breaking of nucleon Cooper pairs is revealed by sequential peaks in the microcanonical caloric curve.
1 More- Received 25 August 2014
- Revised 21 October 2014
DOI:https://doi.org/10.1103/PhysRevC.90.054330
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