Entropy in hot ^{161,162}Dy and ^{171,172}Yb nuclei

Abstract

The density of accessible levels at low spin in the (^3He,αγ) reaction has been extracted for the ^{161,162}Dy and ^{171,172}Yb nuclei. The entropy of the even-odd and even-even nuclei has been deduced as a function of excitation energy, and found to reach a maximum of 15 k_B before neutron evaporation. The entropy of one quasi-particle outside an even-even core is found to be 1.70(15) k_B. This quasi-particle picture of hot nuclei is well accounted for within a simple pairing model. The onset of two, four and six quasi-particle excitations in the ^{162}Dy and ^{172}Yb nuclei is discussed and compared to theory. The number of quasi-particles excited per excitation energy is a measure for the ratio of the level energy spacing and the pairing strength.

19 pages, 11 figures

References in corpus (3)

• Extraction of level density and gamma strength function from primary gamma spectra
• Phase Transitions in "Small" systems
• Particle-Number Reprojection in the Shell Model Monte Carlo Method: Application to Nuclear Level Densities

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• Thermal nuclear pairing within the self-consistent quasiparticle RPA