Evidence for a “singularity” in the nuclear rotational band structure

Johnson, A.; Ryde, H.; Sztarkier, J.

doi:10.1016/0370-2693(71)90150-x

Cited by 280 publications

(105 citation statements)

References 8 publications

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“…A sudden increase of a nuclear moment of inertia in yrast rotational band at some critical angular momentum or rotational frequency, discovered few decades ago [1], continues to attract a considerable attention. There is a general persuasion that this phenomenon is a result of the rotational alignment of angular momenta of a nucleon pair occupying a high-j intruder orbital near the Fermi surface (see textbooks [2,3] and references therein).…”

Section: Introductionmentioning

confidence: 99%

Microscopic analysis of shape-phase transitions in even-evenN~90rotating nuclei

Kvasil

Nazmitdinov

2006

Phys. Rev. C

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We study in cranked Nilsson plus random phase approximation shape transitions in fast rotating nuclei undergoing backbending, more specifically 156 Dy and 162 Yb. We found that a backbending in 156 Dy is correlated with the disappearance of the collective, positive signature γ-vibrational mode in the rotating frame, and, a shape transition (axial→ nonaxial) is accompanied with a large acquiring of the γ deformation. We show that such a shape transition can be considered as a phase transition of the first order. In 162 Yb the quasiparticle alignment dominates in the backbending and the shape transition (axial→ nonaxial) is accompanied with a smooth transition from zero to nonzero values of the γ deformation. We extend the classical Landau theory for rotating nuclei and show that the backbending in 162 Y b is identified with the second order phase transition. A description of spectral and decay properties of the yrast states and low-lying excitations demonstrates a good agreement between our results and experimental data.

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Section: Introductionmentioning

confidence: 99%

Microscopic analysis of shape-phase transitions in even-evenN~90rotating nuclei

Kvasil

Nazmitdinov

2006

Phys. Rev. C

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“…This behavior causes back-bending in the curve of 2 / 2 when plotted versus the square of the energy 2 ) ( [25].…”

Section: Methods and Calculationsmentioning

confidence: 99%

Microscopic description of energy-levels for even-even 124-134Xe isotopes

Ahmed

2017

AIP Conference Proceedings

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Abstract.The first measured excited states 1 2 E and the ratio of the second to the first measured excited states, the back-bending, the E-GOS and the ratio among the energies of the (I+2) and (I) states as a function of the spin (I) have been drawn to determine the properties of the ground-states band. The odd-even staggering has been drawn to determine the difference between the energies of ground states band (GSB) and negative parity band (NPB). Bohr-Mottelson Model ( BM ), Interacting Boson Model ( IBM-1 ), Interacting Vector Boson Model ( IVBM ) and Doma-El-Gendy (D-G) relation have been used to calculate the energy levels of (GSB), IBM-1 has been used to calculate the energy of the gamma band (GB), while IVBM and BM have been used to calculate the energy levels of (NPB). The calculated energy levels in comparison with the measured data indicated the quality of the fitness presented in this work.

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“…Rotational excitations in atomic nuclei have long been a source of information about the underlying nucleonic structure. A dramatic increase in apparent moment of inertia, known as backbending, was first discovered [1] in 160 Dy at an angular momentum of I ഠ 16h, and is now well established as a general feature of nuclear rotation. In well deformed, axially symmetric nuclei, backbending has been understood [2] to be due to the alignment of the angular momentum of a pair of high-j nucleons along the rotation axis, so that the mean angular-momentum component along the symmetry axis (perpendicular to the rotation axis) is ͗K͘ ഠ 0.…”

Section: (Received 13 February 1997)mentioning

confidence: 99%

Tilted Rotation and Backbending in an Odd-Proton Nucleus

et al. 1997

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Tilted-axis rotation, arising from Fermi-aligned configurations, has been observed for the first time to cause backbending in an odd-proton nucleus. In 181 Re, two t-bands are found to be energetically favored relative to the usual rotation-aligned s-bands, presenting an alternative form of cold nuclear rotation. Interactions between the bands are weak, and unambiguous comparisons with tilted-axiscranking calculations can be made. [S0031-9007(97) PACS numbers: 21.10. Re, 21.10.Jx, 23.20.Gq, 27.70. + q Rotational excitations in atomic nuclei have long been a source of information about the underlying nucleonic structure. A dramatic increase in apparent moment of inertia, known as backbending, was first discovered [1] in 160 Dy at an angular momentum of I ഠ 16h, and is now well established as a general feature of nuclear rotation. In well deformed, axially symmetric nuclei, backbending has been understood [2] to be due to the alignment of the angular momentum of a pair of high-j nucleons along the rotation axis, so that the mean angular-momentum component along the symmetry axis (perpendicular to the rotation axis) is ͗K͘ ഠ 0. The aligned structure (s-band) becomes favored in energy at high spin and crosses the nonaligned structure (g band).In the A ഠ 180 mass region, where backbending is due to a pair of i 13͞2 neutrons, it has been proposed [3,4] that a new structure arises due to the Fermi-aligned [4,5] coupling scheme which is active in the middle of the neutron shell (N ഠ 104). In this scheme the nucleon angular-momentum precesses about an axis lying between the rotation and symmetry axes. The projections of the angular momentum onto the symmetry axis, K, and the rotation axis, i, are both localized at a nonzero value. This differs from the strong-coupling scheme in which the nucleon angular-momentum precesses about the nuclear symmetry axis resulting in good K, with ͗i͘ ഠ 0. States formed from a pair of Fermi-aligned nucleons have K ഠ jK 1 6 K 2 j and i ഠ i 1 1 i 2 , resulting in the usual s states, having K ഠ 0, and also t states having large K and a total angular momentum tilted between the rotation and symmetry axes. The s-and t-bands compete for "yrast" status (the lowest energy for a given angular momentum) corresponding to cold nuclear rotation. The nature and extent of this competition is not yet understood, and the possibility of there being large-amplitude high-K components in the yrast bands of nuclei with N ഠ 104 is contrary to the usual interpretation of backbending as intrinsically a low-K phenomenon.Evidence for the role of t-band structures in backbending has been observed in 179,180 W [3,6] and 181,182 Os [7] (with proton numbers Z 74, 76, respectively). However, only in 179 W are the band interactions sufficiently weak to enable a clear signature to be obtained of the high-K band crossing, and in this unique case a chance near degeneracy at the band crossing could be responsible for the special features. Furthermore, rotational models [4] have failed to reproduce the band crossings in 1...

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Evidence for a “singularity” in the nuclear rotational band structure

Cited by 280 publications

References 8 publications

Microscopic analysis of shape-phase transitions in even-evenN~90rotating nuclei

Microscopic analysis of shape-phase transitions in even-evenN~90rotating nuclei

Microscopic description of energy-levels for even-even 124-134Xe isotopes

Tilted Rotation and Backbending in an Odd-Proton Nucleus

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