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Frattini, S.; Bracco, A.; Leoni, S.; Bosetti, P.; Herskind, B.; Døssing, T.; Bergström, M.; Hagemann, G.B.; Ryde, H.; Vivien, J.P.; Bagshow, A; Smalley, D.H.; Smith, A. G.

doi:10.1103/physrevlett.81.2659

Cited by 14 publications

(28 citation statements)

References 17 publications

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“…The analysis supports the SD nature of the excited rotational bands. This shows that the SD nucleus maintains its collectivity with increasing excitation energy, at least until rotational damping sets in, as predicted by the cranked shell model calculations of Yoshida et al [92], and also observed in ND nuclei [175,83]. Second, angular distributions can be performed.…”

Section: Rotation Tunnelling and Ergodic Bands At High Temperaturesupporting

confidence: 66%

“…2.1.4. f (x − x 0 , y − y 0 ) is a two dimensional normalized Gaussian weighting function and F it(x, y) is a polynomial fit to the local data, typically a 7 × 7 area of the matrix around the point of interest (in the case of a 4 keV/ch spectrum binning). The fluctuation analysis method was originally developed and employed to study warm rotation in normal deformed nuclei [68,82,83,84,85]. Extensive investigations were performed also in connection with specific nuclear configurations, such as low-K/high-K structures for the study of the transition between order and chaos in the atomic nucleus [86,87,88,89,90].…”

Section: Fluctuation Analysismentioning

confidence: 99%

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Population and decay of superdeformed nuclei probed by discrete and quasi-continuum γ-ray spectroscopy

Лопез-Мартенс

Lauritsen

Leoni

et al. 2016

Progress in Particle and Nuclear Physics

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Nuclear superdeformation at high spin was discovered a little over 30 years ago. Since then, a large body of data has been collected on the subject and many new and interesting phenomena have been discovered. In particular, the way superdeformed states are populated and depopulated offers a unique laboratory to study rotational motion as a function of excitation energy and the evolution of nuclear structure over a large interval in energy and spin. This article focusses on the experimental techniques and methods developed to study the quasicontinuous spectra of gamma rays emitted by rapidly rotating superdeformed nuclei and presents the results regarding rotational damping, the transition from ordered to chaotic motion and quantum tunnelling in a complex environment.

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Section: Rotation Tunnelling and Ergodic Bands At High Temperaturesupporting

confidence: 66%

Section: Fluctuation Analysismentioning

confidence: 99%

Population and decay of superdeformed nuclei probed by discrete and quasi-continuum γ-ray spectroscopy

Лопез-Мартенс

Lauritsen

Leoni

et al. 2016

Progress in Particle and Nuclear Physics

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“…The experimental analysis has shown that the majority of γ rays emitted in heavy-ion fusion reactions leading to deformed nuclei are of rotational nature. They are associated with a lifetime typical of strongly collective transitions [5] and produce γ -γ coincidence spectra characterized by a typical ridge-valley structure [4]. Such a landscape carries information both on the decay along discrete rotational bands at relatively low excitation energies above yrast (ridges) and on the more excited strongly interacting bands (valley), corresponding to states of typical excitation energies 1 to 2 MeV above yrast.…”

Section: Introductionmentioning

confidence: 99%

Damping mechanisms and order-to-chaos transition in the warm rotatingEr163nucleus

Leoni¹,

Bracco²,

Blasi³

et al. 2005

Phys. Rev. C

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The γ decay in the quasicontinuum is used to study the order-to-chaos transition in the thermally excited 163 Er nucleus. The experimental analysis is performed on high-statistics EUROBALL data, focusing on the spin region I ≈ (20-40)h, and internal excitation energy up of ≈2.5 MeV. The results are compared to cranked shell model calculations for this nucleus, taking into account the dependence on the K quantum number. Two main topics are investigated. First, the validity of the selection rules associated with the K quantum number are studied as a function of the internal energy U above yrast. K-selection rules are found to be obeyed in the decay along discrete unresolved rotational bands up to U ≈ 1.2 MeV, whereas in the interval U ≈ 1.2-2.5 MeV, where the order-to-chaos transition is expected to take place, selection rules are found to be only partially valid. Second, the line-shape analysis of γ -γ coincidence spectra provides a direct experimental measurement of the rotational and compound damping widths ( rot and µ ), yielding values of 200 and 20 keV, respectively, in good agreement with theory.

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“…In the case of the 164 Yb data the comparison is made with the available calculations for 168 Yb which describe the average features of the quasicontinuum of rare-earth nuclei (cf. [10] and [12]). …”

mentioning

confidence: 99%

“…Energydependent time gates on the Ge time signal were used to suppress the background from neutrons. The data for the nucleus 164 Yb, which are discussed in comparison with the 114 Te data, were obtained in a previous measurement made with the array EUROGAM II [10] using the reaction 30 Si 1 138 Ba at bombarding energies of 140, 145, 150, and 155 MeV. The maximum angular momentum for the Te case was calculated by the Winther model [11] including the collective degree of freedom in the fusion process to be 56h, 61h, 67h, 71h, and 74h, respectively.…”

mentioning

confidence: 99%

UnresolvedγRays in114Te: Mass Dependence of Rotational Damping

et al. 1999

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Unresolved g rays of 114 Te sorted into one-and two-dimensional spectra were studied. The reaction 64 Ni͑E beam 230 270 MeV͒ 1 54 Cr was used and the g rays were detected with the EUROBALL array. The effective moment of inertia for the quasicontinuum was found to be almost constant for I ͑20 40͒h, in contrast with the decreasing behavior of the terminating yrast band. A comparative analysis with the nucleus 164 Yb is presented and the results from a fluctuation analysis were compared with cranked shell model calculations. The comparison shows consistency in the scaling of the rotational damping width with mass number.PACS numbers: 21.10. Re, 21.60.Ka, 23.20.Lv, 27.60. + j The understanding of rotational motion in thermally excited nuclei is one of the central issues in nuclear structure and more in general in the study of effects beyond mean field. Until now, convincing evidence of collective damped rotation has been obtained for the mass region A ഠ 160. The overall features of quasicontinuum spectra have been well described with the rotational damping model calculations in which the mean-field rotational bands of the cranked shell model are mixed by the residual two-body interaction [1]. In the original formulation of rotational damping [2], schematic estimates for the scaling of the mixing process of mean-field bands with mass number were derived. The energy U 0 relative to the yrast line, at which the damping (mixing) sets in, depends on the level density and on the strength of the residual interaction, and is predicted to vary with mass number U 0~A 22͞3 . The rotational damping width G rot , expressing the width of the quadrupole transition strength distribution, is proportional to the statistical dispersion of the rotational frequency of cranked shell model n-particle-n-hole states. For G rot the scaling is expected to follow the relation G rotĨ A 25͞2 e 21 , where I, A, and e are the spin, mass number, and deformation, respectively. Experiments have earlier confirmed the prediction of U 0 ഠ 0.7 MeV for the onset of damping in rare-earth nuclei [3]. However, the damping width G rot appears to be a quantity not easily accessible in experiments [4]. Experimentally, its variation with mass number for normally deformed nuclei has never been investigated. On the other hand, a detailed test of effects beyond mean field such as the rotational damping mechanism is also relevant in view of the analogy discussed in Ref.[5] with nuclear magnetic resonance. To determine the validity of the relation given above, one needs to compare nuclei with a similar deformation, but with different masses; good examples are nuclei with A ഠ 160 and A ഠ 110 for which a factor of 2 difference in the damping width is expected.Some evidence of collective rotation in the quasicontinuum in nuclei with A 110 120, characterized by spherical shapes at low spins, was found two decades ago in experiments made with scintillator detectors [6]. More recent discrete spectroscopy studies made with multigermanium detector arrays have identified di...

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Rotational Quadrupole Moment of Thermally Excited High Spin States inY164b

Cited by 14 publications

References 17 publications

Population and decay of superdeformed nuclei probed by discrete and quasi-continuum γ-ray spectroscopy

Population and decay of superdeformed nuclei probed by discrete and quasi-continuum γ-ray spectroscopy

Damping mechanisms and order-to-chaos transition in the warm rotatingEr163nucleus

UnresolvedγRays in114Te: Mass Dependence of Rotational Damping

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