Nonzero Quadrupole Moments of Candidate Tetrahedral Bands

Bark, R. A.; Sharpey‐Schafer, J. F.; Maliage, S. M.; Madiba, T. E.; Komati, F.; Lawrie, E. A.; Lawrie, J. J.; Lindsay, R.; Maine, P.; Mullins, S. M.; Murray, S. H. T.; Ncapayi, N. J.; Ramashidza, T.M.; Smit, F. D.; Vymers, P.

doi:10.1103/physrevlett.104.022501

Cited by 32 publications

(58 citation statements)

References 30 publications

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“…The most favourable region for observing tetrahedral states is in the mass region of A ∼ 160 [569]. Measurements of quadrupole moments of low-lying negative-parity bands in this region have not supported the tetrahedral hypothesis [570]. It was found, however, that the experimental systematics of the the dipole (E1) γ-transitions [473] are in good agreement with the increasing triaxial quadrupole deformation [563,565].…”

Section: Shape Transitions In Rotating Nucleimentioning

confidence: 92%

Effects of symmetry breaking in finite quantum systems

2013

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The review considers the peculiarities of symmetry breaking and symmetry transformations and the related physical effects in finite quantum systems. Some types of symmetry in finite systems can be broken only asymptotically. However, with a sufficiently large number of particles, crossover transitions become sharp, so that symmetry breaking happens similarly to that in macroscopic systems. This concerns, in particular, global gauge symmetry breaking, related to Bose-Einstein condensation and superconductivity, or isotropy breaking, related to the generation of quantum vortices, and the stratification in multicomponent mixtures. A special type of symmetry transformation, characteristic only for finite systems, is the change of shape symmetry. These phenomena are illustrated by the examples of several typical mesoscopic systems, such as trapped atoms, quantum dots, atomic nuclei, and metallic grains. The specific features of the review are: (i) the emphasis on the peculiarities of the symmetry breaking in finite mesoscopic systems; (ii) the analysis of common properties of physically different finite quantum systems; (iii) the manifestations of symmetry breaking in the spectra of collective excitations in finite quantum systems. The analysis of these features allows for the better understanding of the intimate relation between the type of symmetry and other physical properties of quantum systems. This also makes it possible to predict new effects by employing the analogies between finite quantum systems of different physical nature.

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Section: Shape Transitions In Rotating Nucleimentioning

confidence: 92%

Effects of symmetry breaking in finite quantum systems

2013

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“…Recently, lots of theoretical studies focus on this nuclear shape, either from the T D d -symmetric single particle spectra [7,[9][10][11] or from various nuclear models including the macroscopicmicroscopic model [9,[11][12][13], the Skyrme Hartree-Fock (SHF), SHF+BCS, or Skyrme Hartree-Fock-Bogoliubov models [11][12][13][14][15][16][17][18], and the Reflection Asymmetric Shell Model (RASM) [19,20]. In particular, Dudek et al predicted that a negative-parity band in 156 Gd is a favorable candidate to manifest tetrahedral symmetry [13] which has stimulated several interesting experimental studies [21,22].Nowadays the study of nuclei with Z ∼ 100 becomes more and more important because it not only reveals the structure of these nuclei themselves but also provides significant information for superheavy nuclei [23][24][25][26]. One of the relevant and interesting topics is how to explain the * sgzhou@itp.ac.cn low-lying 2 − states in some N = 150 even-even nuclei.…”

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confidence: 99%

Nonaxial-octupoleY32correlations inN=150isotones from multidimensional constrained covariant density functional theories

et al. 2012

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The non-axial reflection-asymmetric β32 shape in some transfermium nuclei with N = 150, namely 246 Cm, 248 Cf, 250 Fm, and 252 No are investigated with multidimensional constrained covariant density functional theories. By using the density-dependent point coupling covariant density functional theory with the parameter set DD-PC1 in the particle-hole channel, it is found that, for the ground states of 248 Cf and 250 Fm, the non-axial octupole deformation parameter β32 > 0.03 and the energy gain due to the β32 distortion is larger than 300 keV. In 246 Cm and 252 No, shallow β32 minima are found. The occurrence of the non-axial octupole β32 correlations is mainly from a pair of neutron orbitals [734]9/2 (νj 15/2 ) and [622]5/2 (νg 9/2 ) which are close to the neutron Fermi surface and a pair of proton orbitals [521]3/2 (πf 7/2 ) and [633]7/2 (πi 13/2 ) which are close to the proton Fermi surface. The dependence of the non-axial octupole effects on the form of energy density functional and on the parameter set is also studied.PACS numbers: 21.10. Dr, 21.60.Jz, 27.90.+b The majority of observed nuclear shapes is of spheroidal form which is usually described by β 20 . The existence of the nonaxial-quadrupole (triaxial) deformation β 22 [1-3] and the axial octupole deformation β 30 [4] in atomic nuclei have also been confirmed both experimentally and theoretically. However, there is no a priori reason to neglect the nonaxial-octupole deformations, especially the β 32 deformation [5][6][7]. The pure β 32 deformation has a tetrahedral symmetry with a symmetry group T D d . The existence of non-trivial irreducible representations of this group makes it possible for a nuclei to have large energy gaps in their single-particle levels, thus increasing it's stability [8]. It has been anticipated that β 32 deformation occurs in the ground states of some nuclei with special combinations of the neutron and proton numbers [7][8][9]. Recently, lots of theoretical studies focus on this nuclear shape, either from the T D d -symmetric single particle spectra [7,[9][10][11] or from various nuclear models including the macroscopicmicroscopic model [9,[11][12][13], the Skyrme Hartree-Fock (SHF), SHF+BCS, or Skyrme Hartree-Fock-Bogoliubov models [11][12][13][14][15][16][17][18], and the Reflection Asymmetric Shell Model (RASM) [19,20]. In particular, Dudek et al. predicted that a negative-parity band in 156 Gd is a favorable candidate to manifest tetrahedral symmetry [13] which has stimulated several interesting experimental studies [21,22].Nowadays the study of nuclei with Z ∼ 100 becomes more and more important because it not only reveals the structure of these nuclei themselves but also provides significant information for superheavy nuclei [23][24][25][26]. One of the relevant and interesting topics is how to explain the * sgzhou@itp.ac.cn low-lying 2 − states in some N = 150 even-even nuclei. In these nuclei, the bandhead energy E(2 − ) of the lowest 2 − bands is very low [27]. It is well accepted that the octupole correlation...

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“…Generally, these studies are inconclusive since: a) the existence of global tetrahedral minima was rare and model-dependent b) contradictory results were obtained within the same models. Similar ambiguity occurs also in experiments which so far either did not give a clear evidence [25] or even gave a strong evidence against tetrahedral symmetry [26,27]. For example, negative-parity bands in 156 Dy, observed quite recently [28], are most likely related to the octupole excitations rather than the exotic tetrahedral symmetry.…”

Section: Introductionmentioning

confidence: 63%

Test of Tetrahedral Symmetry for Heavy and Superheavy Nuclei

Jachimowicz

Rozmej

Kowal

et al. 2011

Int. J. Mod. Phys. E

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We search for effects of tetrahedral deformation β32 over a range of ∼ 3000 heavy and superheavy nuclei, 82 ≤ Z ≤ 126, using a microscopic-macroscopic model based on the deformed Woods-Saxon potential, well tested in the region. We look for the energy minima with a non-zero tetrahedral distortion, both absolute and conditional -with the quadrupole distortion constrained to zero. In order to assure reliability of our results we include 10 most important deformation parameters in the energy minimization. We could not find any cases of stable tetrahedral shapes. The only sizable -up to 0.7 MeV -lowering of the ground state occurs in superheavy nuclei Z ≥ 120 for N = 173−188, as a result of a combined action of two octupole deformations: β32 and β30, in the ratio β32/β30 ≈ 3/5. The resulting shapes are moderately oblate, with the superimposed distortion β33 with respect to the oblate axis, which makes the equator of the oblate spheroid slightly triangular. Almost all found conditional minima are excited and not protected by any barrier; a handful of them are degenerate with the axial minima. * Electronic address: michal.kowal@ncbj.gov.pl

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Nonzero Quadrupole Moments of Candidate Tetrahedral Bands

Cited by 32 publications

References 30 publications

Effects of symmetry breaking in finite quantum systems

Effects of symmetry breaking in finite quantum systems

Nonaxial-octupoleY32correlations inN=150isotones from multidimensional constrained covariant density functional theories

Test of Tetrahedral Symmetry for Heavy and Superheavy Nuclei

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