Instantaneous shape sampling: A model for the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>γ</mml:mi></mml:mrow></mml:math>-absorption cross section of transitional nuclei

Bentley, Ian; Brant, S.; Dönau, F.; Frauendorf, S.; Kämpfer, B.; Schwengner, R.; Zhang, S. Q.

doi:10.1103/physrevc.83.014317

Cited by 7 publications

(8 citation statements)

References 51 publications

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“…In an early relevant study [49] these two components are documented to both have their origin in work of Landau; this is why we avoid to connect one of them with his name. In the list of origins for the IVGDR widening in section 4 we list these two contributions under (c) and (a), respectively; for the one body term we use the previously proposed [167] expression fragmentation. Under (b) we have a separate component for nuclear shape induced splitting, which when added to the others may eventually be confused with fragmentation caused by shell effects.…”

Section: Microscopic Descriptions Of the Ivgdrmentioning

confidence: 99%

“…The aspect of triaxiality was also regarded [167] and related to IVGDR's in about 20 not strongly deformed nuclei by introducing values for β and γ from an IBAanalysis of spectroscopic data into a QRPA calculation; an ISS treatment similar to the one described in section 4 was applied. The calculations result in a considerable fragmentation and a comparison to experimental IVGDR data was made only for 5 Sm-isotopes after a folding with an energy dependent Lorentzian width of approximately 2.5 MeV, apparently selected arbitrarily; the agreement is difficult to judge because of a small linear scale, but it seems reasonable.…”

Section: Microscopic Descriptions Of the Ivgdrmentioning

confidence: 99%

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Breaking of axial symmetry in excited heavy nuclei as identified in giant dipole resonance data

2017

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Abstract. A recent theoretical prediction of a breaking of axial symmetry in quasi all heavy nuclei is confronted to a new critical analysis of photon strength functions of nuclei in the valley of stability. For the photon strength in the isovector giant dipole resonance (IVGDR) regime a parameterization of GDR shapes by the sum of three Lorentzians (TLO) is extrapolated to energies below and above the IVGDR. The impact of non-GDR modes adding to the low energy slope of photon strength is discussed including recent data on photon scattering and other radiative processes. These are shown to be concentrated in energy regions where various model calculations predict intermediate collective strength; thus they are obviously separate from the IVGDR tail. The triple Lorentzian (TLO) ansatz for giant dipole resonances is normalized in accordance to the dipole sum rule. The nuclear droplet model with surface dissipation accounts well for positions and widths without local, nuclide specific, parameters. Very few and only global parameters are needed when a breaking of axial symmetry already in the valley of stability is admitted and hence a reliable prediction for electric dipole strength functions also outside of it is expected.

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Section: Microscopic Descriptions Of the Ivgdrmentioning

confidence: 99%

Section: Microscopic Descriptions Of the Ivgdrmentioning

confidence: 99%

Breaking of axial symmetry in excited heavy nuclei as identified in giant dipole resonance data

2017

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“…These calculations take into account quadrupole and triaxial deformation and are therefore suitable for the present task. The QRPA is based on a Wood-Saxon mean field and an isovector dipole-dipole interaction [26]. For the calculation of the low-energy part of the PSF the suppression of the spurious center-of-mass motion was performed as described in Ref.…”

mentioning

confidence: 99%

“…calculations are described in Ref. [26,31], where the deformation parameters β 2 , which result from the micromacro mean field calculations, are quoted. These values are consistent with the experimental ones given in Ref.…”

mentioning

confidence: 99%

Nuclear Deformation and Neutron Excess as Competing Effects for Dipole Strength in the Pygmy Region

Massarczyk¹,

Schwengner²,

Dönau³

et al. 2014

Phys. Rev. Lett.

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The electromagnetic dipole strength below the neutron-separation energy has been studied for the xenon isotopes with mass numbers A = 124, 128, 132, and 134 in nuclear resonance fluorescence experiments using the γELBE bremsstrahlung facility at Helmholtz-Zentrum Dresden-Rossendorf and the HIγS facility at Triangle Universities Nuclear Laboratory Durham. The systematic study gained new information about the influence of the neutron excess as well as of nuclear deformation on the strength in the region of the pygmy dipole resonance. The results are compared with those obtained for the chain of molybdenum isotopes and with predictions of a random-phase approximation in a deformed basis. It turned out that the effect of nuclear deformation plays a minor role compared with the one caused by neutron excess. A global parametrization of the strength in terms of neutron and proton numbers allowed us to derive a formula capable of predicting the summed E1 strengths in the pygmy region for a wide mass range of nuclides. Photon strength functions (PSF) are important inputs for statistical reaction codes applied in network calculations in nuclear astrophysics and in simulations done for nuclear power production and safety. Knowing and understanding the behavior of the PSF in the energy region around and below the neutron threshold is essential for these applications. For the dominating electric dipole (E1) part of the PSF, the RIPL3 compilation of the IAEA [1] offers an overview on various models, which in essence base on the concept of the damped isovector E1 giant dipole resonance (GDR). It is described by one or two Lorentzian functions with parameters fitted to the characteristic resonance structure observed in (γ, n) reactions. For open shell nuclei, which constitute the majority, the nuclear deformation is taken into account. It splits the peak of the GDR [2, 3] and, as a consequence, increases the dipole strength distribution in the region below the neutron-separation energy. Along these lines, a new global description of the PSF was recently presented in Ref.[4], which takes triaxial quadrupole deformation into account and which is called triple Lorentzian model (TLO).Experimental and theoretical studies [5][6][7][8][9], which have been recently reviewed by Savran, Aumann, and Zilges [10] suggest a richer structure of the PSF below the neutron-separation energy than accounted for by the Lorentzian-type models. In this letter we follow the suggestion in the review [10]: "Today the term Pygmy Dipole Resonance (PDR) is frequently used for the low-lying E1 strength and we will follow this notation in this review without implying with this notation any further interpretation of its structure." The rational behind this terminology is that the interpretation of the PDR depends strongly on the theoretical model invoked and present day experiments cannot distinguish between the models. One important aspect of studying the PDR concerns its isospin dependence, which is particularly important for simulating the r-process that d...

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“…Recently work was published [25] where ground-state deformation parameters β and γ for stable Kr, Xe, Ba, and Sm isotopes were calculated using the eigenvalues of corresponding IBA-1 calculations, and the resulting modifications of the equilibrium deformations as taken from LDM compilations [19] were listed. With the exception of two well deformed nuclei γ-values between 17 and 30 deg found and this may be considered an indication of triaxiality, be it static or dynamic.…”

Section: Level Energies and Transition Ratesmentioning

confidence: 99%

Experimental Signals for Broken Axial Symmetry in Excited Heavy Nuclei from the Valley of Stability

Grosse¹,

Junghans²

2018

Acta Phys. Pol. B Proc. Suppl.

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An increasing number of experimental data indicates the breaking of axial symmetry in many heavy nuclei already in the valley of stability: Multiple Coulomb excitation analysed in a rotation invariant way, gamma transition rates and energies in odd nuclei, mass predictions, the splitting of Giant Resonances (GR), the collective enhancement of nuclear level densities and Maxwellian averaged neutron capture cross sections. For the interpretation of these experimental observations the axial symmetry breaking shows up in nearly all heavy nuclei as predicted by Hartree-Fock-Bogoliubov (HFB) calculations [1] ; this indicates a nuclear Jahn-Teller effect. We show that nearly no parameters remain free to be adjusted by separate fitting to level density or giant resonance data, if advance information on nuclear deformations, radii etc. are taken from such calculations with the force parameters already fixed. The data analysis and interpretation have to include the quantum mechanical requirement of zero point oscillations and the distinction between static vs. dynamic symmetry breaking has to be regarded. PACS numbers: PACS numbers come here(1)

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Instantaneous shape sampling: A model for theγ-absorption cross section of transitional nuclei

Cited by 7 publications

References 51 publications

Breaking of axial symmetry in excited heavy nuclei as identified in giant dipole resonance data

Breaking of axial symmetry in excited heavy nuclei as identified in giant dipole resonance data

Nuclear Deformation and Neutron Excess as Competing Effects for Dipole Strength in the Pygmy Region

Experimental Signals for Broken Axial Symmetry in Excited Heavy Nuclei from the Valley of Stability

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