The role of seniority-zero states in nuclear level densities

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At low excitation energies seniority-zero states dominate the level density of K = 0 bands in deformed even even nuclei, while they play no role at higher excitation energies. We describe the level densities in a Fermi-gas model as well as in a combinatorial level-density model and compare to detailed experimental data for some rare-earth nuclei. An explanation is provided for recent observations of an odd even staggering in the spin-distribution function as an effect of r-symmetry of wave functions for deformed nuclei. The structure of 0(+) states in deformed nuclei is discussed in the model and compared to data, stressing the role of the seniority quantum number. The Fermi-gas model is utilized to obtain an overview of the odd even staggering phenomenon in other mass regions. Odd even staggering in spherical nuclei, appearing in open-shell nuclei, is briefly discussed as caused by fermion exchange symmetry. (C) 2015 Elsevier B.V. All rights reserved.


Enheter & grupper
Externa organisationer
  • Niels Bohr Institute
  • Los Alamos National Laboratory

Ämnesklassifikation (UKÄ) – OBLIGATORISK

  • Subatomär fysik


Sidor (från-till)97-120
TidskriftNuclear Physics, Section A
StatusPublished - 2015
Peer review utfördJa