Inconsistencies in the description of pairing effects in nuclear level densities

Abstract

Pairing correlations have a strong influence on nuclear level densities. Empirical descriptions and theoretical models have been developed to take these effects into account. The present article discusses cases, where descriptions of nuclear level densities are inconsistent or in conflict with the present understanding of nuclear properties. Phenomenological approaches consider a back-shift parameter. However, the absolute magnitude of the back-shift, which actually corresponds to the pairing condensation energy, is generally not compatible with the observation that stable pairing correlations are present in essentially all nuclei. It is also shown that in the BCS model pairing condensation energies and critical pairing energies are inconsistent for light nuclei. A modification to the composite Gilbert-Cameron level-density description is proposed, and the use of more realistic pairing theories is suggested.

17 pages, 3 figures

References in corpus (6)

• Final excitation energy of fission fragments
• Nuclear level densities and gamma-ray strength functions in 44,45Sc
• Thermodynamics of pairing in mesoscopic systems
• Cooper pairs in atomic nuclei
• Thermodynamics of nuclei in thermal contact
• Microscopic calculation of symmetry projected nuclear level densities

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