Nature of Low-Energy Dipole Strength in Nuclei: The Case of a Resonance at Particle Threshold in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mmultiscripts><mml:mi mathvariant="normal">P</mml:mi><mml:mprescripts /><mml:none /><mml:mn mathvariant="normal">208</mml:mn></mml:mmultiscripts><mml:mi mathvariant="normal">b</mml:mi></mml:math>

Ryezayeva, N.; Hartmann, T.; Kalmykov, Y.; Lenske, H.; Neumann-Cosel, P. von; Ponomarev, V. Yu.; Richter, A.; Shevchenko, A.; Volz, S.; Wambach, J.

doi:10.1103/physrevlett.89.272502

Cited by 291 publications

(381 citation statements)

References 39 publications

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“…However, we have a large disagreement with experimental data at E < 5 MeV. As one can see from [16], where the transitions between ground end excited states have been measured, the beginning of the 1 − excitation spectrum in [16] is 4.84 MeV, i.e. there is no 1 − transitions between ground and excited states below 4.84 MeV.…”

Section: Photon Strength Functionscontrasting

confidence: 67%

“…It is necessary to compare both sets of data with approximately the same smoothing. So, taking into account that the experimental resolution in the experimental data [13] is about 200 keV, we smoothed the data [16] with three smoothing parameters 100 keV, 200 keV, and 400 keV. As it can be expected, we obtained a rough agreement between both sets of experimental data at E > 4.84 MeV.…”

Section: Photon Strength Functionssupporting

confidence: 60%

“…The results obtained confirm the necessity of using consistent microscopic approaches for calculations of radiative nuclear characteristics in double-magic nuclei. Also, due to comparison of the two sets of experimental data [13] and [16], it was possible to conclude that the nature of the PSF values observed in [16] at E < 4.84 MeV for 208 Pb should be only caused by the transitions between excited states.…”

Section: Resultsmentioning

confidence: 99%

“…Thus, one can think that the excitations observed in [13] at E < 4.84 MeV are only caused by transitions between excited states. However, it is necessary to underline that the mechanisms of the reactions used in [13] and [16] are very different and the use of energy-independent smoothing parameter may be too approximate. …”

Section: Photon Strength Functionsmentioning

confidence: 99%

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Microscopic calculations of the characteristics of radiative nuclear reactions for double-magic nuclei

Achakovskiy

Kamerdzhiev

Tselyaev

et al. 2016

EPJ Web of Conferences

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Abstract. The neutron capture cross sections and average radiative widths Γ γ of neutron resonances for two double-magic nuclei 132 Sn and 208 Pb have been calculated using the microscopic photon strength functions (PSF), which were obtained within the microscopic self-consistent version of the extended theory of finite Fermi systems in the time blocking approximation. For the first time, the microscopic PSFs have been obtained within the fully self-consistent approach with exact accounting for the single particle continuum (for 208 Pb). The approach includes phonon coupling effects in addition to the standard RPA approach. The known Skyrme force has been used. The calculations of nuclear reaction characteristics have been performed with the EM-PIRE 3.1 nuclear reaction code. Here, three nuclear level density (NLD) models have been used: the so-called phenomenological GSM, the EMPIRE specific (or Enhanced GSM) and the microscopical combinatorial HFB NLD models. For both considered characteristics we found a significant disagreement between the results obtained with the GSM and HFB NLD models. For 208 Pb, a reasonable agreement has been found with systematics for the Γ γ values with HFB NLD and with the experimental data for the HFB NLD average resonance spacing D 0 , while for these two quantities the differences between the values obtained with GSM and HFB NLD are of several orders of magnitude. The discrepancies between the results with the phenomenological EGLO PSF and microscopic RPA or TBA are much less for the same NLD model.

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Section: Photon Strength Functionscontrasting

confidence: 67%

Section: Photon Strength Functionssupporting

confidence: 60%

Section: Resultsmentioning

confidence: 99%

Section: Photon Strength Functionsmentioning

confidence: 99%

See 2 more Smart Citations

Microscopic calculations of the characteristics of radiative nuclear reactions for double-magic nuclei

Achakovskiy

Kamerdzhiev

Tselyaev

et al. 2016

EPJ Web of Conferences

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“…(41). In all cases, where one has a continuous channel index c, as for instance the radial coordinate r, this is an integral equation.…”

Section: Relativistic Rpa Formalismmentioning

confidence: 99%

Continuum random-phase approximation for relativistic point coupling models

Daoutidis

Ring

2009

Phys. Rev. C

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Relativistic Continuum Random Phase Approximation (CRPA) is used to investigate collective excitation phenomena in several spherical nuclei along the periodic table. We start from relativistic mean field calculations based on a covariant density functional with density dependent zero range forces. From the same functional an effective interaction is obtained as the second derivative with respect to the density. This interaction is used in relativistic continuum-RPA calculations for the investigation of isoscalar monopole, isovector dipole and isoscalar quadrupole resonances of spherical nuclei. In particular we study the low-lying E1 strength in the vicinity of the neutron evaporation threshold. The properties of the resonances, such as centroid energies and strengths distributions are compared with results of discrete RPA calculations for the same model as well as with experimental data.

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Pygmy dipole strength close to particle-separation energies—The case of the Mo isotopes

Rusev¹,

Grosse²,

Erhard³

et al.

The 2nd International Conference on Nuclear Physics in Astrophysics

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Abstract. The distribution of electromagnetic dipole strength in 92, 98, 100 Mo has been investigated by photon scattering using bremsstrahlung from the new ELBE facility. The experimental data for well separated nuclear resonances indicate a transition from a regular to a chaotic behaviour above 4 MeV of excitation energy. As the strength distributions follow a Porter-Thomas distribution much of the dipole strength is found in weak and in unresolved resonances appearing as fluctuating cross section. An analysis of this quasi-continuum -here applied to nuclear resonance fluorescence in a novel way -delivers dipole strength functions, which are combining smoothly to those obtained from (γ, n)-data. Enhancements at 6.5 MeV and at ∼ 9 MeV are linked to the pygmy dipole resonances postulated to occur in heavy nuclei.PACS. 21.10. .+k Dipole strength in heavy nucleiThe response of nuclei to dipole radiation is of special importance for the synthesis of the chemical elements in the cosmos: Particle thresholds may be crossed in hot or explosive scenarios leading to the production of new nuclides from previously formed heavier ones by dissociation in the thermal photon bath. This is likely to be the main path for the generation of the approximately 30 -40 neutrondeficient nuclides which cannot be produced in neutron capture reactions [1]. For the understanding and modelling of this so-called p-process the dipole strength function up to and near the particle thresholds has to be known accurately [2]. As shown previously [3], details of the dipole strength (now in n-rich nuclei) may as well have large consequences for the r-process path and also s-process branchings are influenced by nuclear excitations [4] induced by thermal photons. The experimental knowledge [5] on dipole strength is reasonably well established for many heavy and medium mass nuclei in the region of the giant dipole resonance (GDR) by (γ, xn) studies, which often also cover the region directly above the neutron threshold S n . At lower energies three features have been discussed to be of importance for processes in high-temperature cosmic environments: a) the fall-off [6-9] of the E1-strength on the low-energy slope of the GDR; b) the E1-strength between the ground-state (gs) and low energy excitations and its proper extension [10-12] into the regime (a); c) the occurrence of additional pygmy-resonances, [3,[13][14][15], which are assumed to be not as broad as the GDR, but wider as compared to the average level distance D -thus forming an intermediate structure enclosing many levels. Their low energy may well enhance their contribution to photo-dissociation processes in spite of their relatively low strength as compared to the GDR. In principle, also M1-transitions contribute to the dipole strength, but the average M1 strength is typically 1-2 orders of magnitude smaller as compared to E1, and they are frequently [1-3] not taken into account. A further approximation has to be introduced to estimate dipole strengths for transitions not connected to the g...

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Nature of Low-Energy Dipole Strength in Nuclei: The Case of a Resonance at Particle Threshold inP208b

Cited by 291 publications

References 39 publications

Microscopic calculations of the characteristics of radiative nuclear reactions for double-magic nuclei

Microscopic calculations of the characteristics of radiative nuclear reactions for double-magic nuclei

Continuum random-phase approximation for relativistic point coupling models

Pygmy dipole strength close to particle-separation energies—The case of the Mo isotopes

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