Rotation of warm nuclei and superdeformation

Leoni, S.; Лопез-Мартенс, А.

doi:10.1088/0031-8949/91/6/063009

Cited by 10 publications

(9 citation statements)

References 126 publications

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“…Particularly challenging is the question how to address the regions where the coherence of the nucleonic motion sets in or disappears. One example is the damping of rotation in "warm nuclei" few MeV above yrast, which is discussed in the contribution to this Focus Issue by S. Leoni and A. Lopez-Martin [61].…”

Section: Discussionmentioning

confidence: 99%

“…The possibility to diagonalize matrices of dimension 10 6 and more makes Shell-Model-like approaches new powerful tools. In their contribution to this Focus Issue [61], S. Leon and A. Lopez-Martens discuss "warm nuclei", which is the region of 2-3 MeV above the yrast line. The large density of bands and their mutual coupling require special techniques for analyzing the data from large arrays of γ ray detectors and new concepts (rotational damping) for interpreting the γ ray spectra emitted by these warm nuclei.…”

Section: Approaches Beyond the Unified Modelmentioning

confidence: 99%

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Beyond the Unified Model

Frauendorf

2018

Phys. Scr.

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The key elements of the Unified Model are reviewed. The microscopic derivation of the Bohr Hamiltonian by means of adiabatic time-dependent mean field theory is presented. By checking against experimental data the limitations of the Unified Model are delineated. The description of the strong coupling between the rotational and intrinsic degrees of freedom in framework of the rotating mean field is presented from a conceptual point of view. The classification of rotational bands as configurations of rotating quasiparticles is introduced. The occurrence of uniform rotation about an axis that differs from the principle axes of the nuclear density distribution is discussed. The physics behind this tilted-axis rotation, unknown in molecular physics, is explained on a basic level. The new symmetries of the rotating mean field that arise from the various orientations of the angular momentum vector with respect to the triaxial nuclear density distribution and their manifestation by the level sequence of rotational bands are discussed. Resulting phenomena, as transverse wobbling, rotational chirality, magnetic rotation and band termination are discussed. Using the concept of spontaneous symmetry breaking the microscopic underpinning of the rotational degrees is refined. † BCS is the acronym of Bardeen, Cooper and Schrieffer, who invented it for describing superconductivity in metals [21]. † "yrast": Swedish "most dizzy". These are the states with the highest angular momentum for given energy, which are the lowest states for given angular momentum . Sometimes the state above the yrast state is referred to as " yrare": Swedish "more dizzy". † We adopt the definition of the D-functions and phase conventions used by Bohr and Mottelson [6] and Rowe [9]. † The sign of q 2 is taken according to the "Lund convention" which is opposite to the "Copenhagen convention" of the Bohr Hamiltonian of Ref.[6]. This unfortunate inconsistency persist in the literature and between section 2 and the following as well.

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Section: Discussionmentioning

confidence: 99%

Section: Approaches Beyond the Unified Modelmentioning

confidence: 99%

Beyond the Unified Model

Frauendorf

2018

Phys. Scr.

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“…The Copenhagen/Milano/Kyoto collaboration carefully studied the progressive decoherence of quantal nuclear rotation, which they called "Rotational Damping". Recently Leoni and Lopez-Martens presented the work in a concise review [4]. The theoretical analysis starts from the single particle configurations in a rotating deformed potential described by the Cranked Shell Model.…”

Section: Rotational Dampingmentioning

confidence: 99%

Decoherence of collective motion in warm nuclei

et al. 2019

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Collective states in cold nuclei are represented by a wave function that assigns coherent phases to the participating nucleons. The degree of coherence decreases with excitation energy above the yrast line because of coupling to the increasingly dense background of quasiparticle excitations. The consequences of decoherence are discussed, starting with the well studied case of rotational damping. In addition to superdeformed bands, a highly excited oblate band is presented as a new example of screening from rotational damping. Suppression of pair correlation leads to incoherent thermal M1 radiation, which appears as an exponential spike (LEMAR) at zero energy in the γ strength function of spherical nuclei. In deformed nuclei a Scissors Resonance appears and LEMAR changes to damped magnetic rotation, which is interpreted as partial restoration of coherence.

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“…On the contrary, when moving away from shell closures, different shapes may compete, and often coexist in the very same nucleus at low spins, in a restricted interval of low excitation energy [1,2]. Shapes of quadrupole symmetric forms are the most abundant, a special class being represented by superdeformed states: they have been experimentally observed next to spherical/oblate excitations at high spin and high energy, even in the proximity of magic numbers [3][4][5].…”

Section: Introductionmentioning

confidence: 99%

Revealing microscopic origins of shape coexistence in the Ni isotopic chain

et al. 2019

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In a two–neutron transfer experiment, performed in Bucharest in July 2016 at sub–Coulomb barrier energy,a photon decay hindered – solely – by a nuclear shape change was identified in the 66Ni nucleus. Such a rare process, at spin zero, was clearly observed before only in actinide nuclei in the 1970’s,where fission isomers were found. The experimental findings on 66Ni have been well reproduced by the Monte Carlo Shell Model Calculations of the Tokyo group, which predict a multifaceted scenario of coexistence of spherical, oblate and prolate shapes in neutron–rich Ni isotopes. The results on 66Ni encouraged a comprehensive gamma–spectroscopy investigation of neutron–rich Ni isotopes, in particular 62Ni and 64–Ni, at IFIN–HH (Bucharest), IPN Orsay and ILL (Grenoble), employing different reaction mechanisms to pin down the wave function composition of selected excited states. The aim is to shed light on the microscopic origin of deformation in neutron–rich Ni nuclei, possibly locating other examples of “shape–isomer–like” structures inthis region.

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Rotation of warm nuclei and superdeformation

Cited by 10 publications

References 126 publications

Beyond the Unified Model

Beyond the Unified Model

Decoherence of collective motion in warm nuclei

Revealing microscopic origins of shape coexistence in the Ni isotopic chain

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