Study of parity-doublet structure in the $^{147}$La nucleus

Abstract : Only a small percentage of know nuclei has spherical symmetry, most of them are deformed. The problem of nuclear deformation was rst investigated in 1952 by the A.A. Bohr [1] who suggested that atomic nuclei can acquire shapes other than spherical through a process called spontaneous symmetry breaking (SSB). Because shapes of atomic nuclei largely depend on the interactions between nucleons, nuclear-deformation studies can provide valuable information on nuclear forces, including the so-called residual interactions, responsible for nuclear deformation. In case of octupole deformation, studied in this work, residual interactions correlate nucleons moving on orbits which dier by three units of angular momentum ( ` = 3), and have dierent parities. If the Fermi level of a nucleus is located between such levels octupole deformation may occur. This happens for aparticular numbers of protons and neutrons, called octupole magic numbers (N;Z = 34; 56; 88; 134). Because the wave functions describing octupole-deformed nuclei do not have well-dened parity in the intrinsic frame, in the laboratory frame one ob- serves specic pattern of excited states, called parity doublet. The aim of the present study was to reinvestigate the presence of octupole deformation in the 147La nucleus. The 147La nuclei were produced in spontaneous ssion of 252Cf and measured using the GAMMASPHERE array of Ge detectors. Taking as a starting point schemes proposed in previous works ([2] and [3]), a new scheme of excited states has been proposed for 147La, in which levels and transitions were arranged into a parity-doublet structure, thanks to newly observed transitions with energies 558.8, 436.5, 421.4 and 414.25 keV. In order to determine spins and parities of levels, angular correlation were analysed. Intensities of transitions allowed the determination of dipole moments and gyromagnetic coecients. The properties of excited levels in 147La, which are consistent with analogous properties observed in octupole-deformed nuclei around 147La, support octupole deformation in 147La.
Type de document :
Communication dans un congrès
6th Workshop on Nuclear Fission and Spectroscopy of Neutron-Rich Nuclei (FISSION 2017), Mar 2017, Chamrousse, France. 〈〉
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Contributeur : Emmanuelle Vernay <>
Soumis le : vendredi 7 avril 2017 - 13:01:18
Dernière modification le : jeudi 11 janvier 2018 - 06:13:10


  • HAL Id : in2p3-01503625, version 1




J. Winiewski, W. Urban, T. Rzaca-Urban, A.G. Smith, J.F. Smith, et al.. Study of parity-doublet structure in the $^{147}$La nucleus. 6th Workshop on Nuclear Fission and Spectroscopy of Neutron-Rich Nuclei (FISSION 2017), Mar 2017, Chamrousse, France. 〈〉. 〈in2p3-01503625〉



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