Nuclear level densities and 
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>γ</mml:mi></mml:math>
-ray strength functions in 
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 isotopes: Impact of Porter-Thomas fluctuations

Markova, M.; Larsen, A. C.; Neumann-Cosel, P. von; Bassauer, S.; Görgen, A.; Guttormsen, M.; Garrote, F. L. Bello; Berg, H. C.; Bjørøen, M. M.; Gjestvang, D.; Isaak, J.; Mbabane, M.; Paulsen, W.; Pedersen, L. G.; Pettersen, N. I. J.; Richter, A.; Şahin, E.; Scholz, Philipp; Siem, S.; Tveten, G. M.; Valsdottir, V. M.; Wiedeking, M.

doi:10.1103/physrevc.106.034322

Cited by 10 publications

(2 citation statements)

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“…The pygmy dipole resonance described in detail in the previous section, has also been observed in all the Sn isotopes [64,65] measured using the Oslo method. This method measures the total strength function and cannot distinguish between E1 and M1, so it is assumed that the extra strength on the tail of the GDR is E1 being in the energy range of the pygmy resonance described in the previous section.…”

Section: Nuclear Level Density and Photon Strength Functions Using Th...mentioning

confidence: 59%

AGATA: Nuclear structure advancements with high-energy $$\gamma $$ rays

Camera¹,

Isaak²,

Maj³

et al. 2023

Eur. Phys. J. A

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High-energy $$\gamma $$ γ rays are emitted either in the decay of nuclear discrete states (generally located in the proximity of the particle-emission threshold) or in the electromagnetic decay of collective states. The branching ratio is rather small, therefore in alternative/coincidence with high-energy $$\gamma $$ γ rays one could have neutron or charged-particle emission. The precise measurement of these branching ratios allows a more comprehensive description of the nucleus and, in particular, the selection of the nuclear models which better describes the interplay between the different acting forces and couplings. In the case of the electromagnetic decay of collective states, the precise identification of the populated low-lying states allows the measurement of their wave-function and/or of their ‘bulk’ properties. This information provides, also in this case, a stringent test for the nuclear models. In both cases, to compensate these small branching ratio, a large number of detectors and an accurate selection of a small region of the phase space are needed. AGATA is considered to constitute an optimal array for this kind of measurements. In fact, AGATA, because of its high granularity and its excellent energy resolution, can detect the high-energy $$\gamma $$ γ rays emitted in a specific decay path or associated to specific reaction channels, shapes, deformations. In the introduction, some details on the measurement of high-energy $$\gamma $$ γ rays using HPGe detector are discussed. The sections of this paper focus on the measurements of high-energy $$\gamma $$ γ rays to obtain the photon strength function, the nuclear level density and to identify extreme shapes in highly excited nuclei.

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Section: Nuclear Level Density and Photon Strength Functions Using Th...mentioning

confidence: 59%

AGATA: Nuclear structure advancements with high-energy $$\gamma $$ rays

Camera¹,

Isaak²,

Maj³

et al. 2023

Eur. Phys. J. A

Self Cite

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“…Of course, there are limitations to the shape method since its precision depends on several factors: (1) To what degree the Brink hypothesis is fulfilled, as this hypothesis must be invoked for the internal normalization (sewing technique) of the shape-method data. (2) How high is the initial level density (partial level density)-a low level density can lead to large Porter-Thomas fluctuations, making the internal normalization uncertain [33]. (3) For cases where the spins of the final levels are not the same, a spin distribution must be applied to estimate the ratio R in Eq.…”

Section: Nld Modelmentioning

confidence: 99%

Comprehensive test of nuclear level density models

2022

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For the last two decades, experimental information on nuclear level densities for about 60 different nuclei has been obtained on the basis of the Oslo method. While each of these measurements has been typically compared to one or a few level density models, a global study including all the measurements has been missing. The present study provides a systematic comparison between Oslo data and six global level density models for 42 nuclei for which s-wave resonance spacings are also available. We apply a coherent normalization procedure to the Oslo data for each of the six different models, all being treated on the same footing. Our quantitative analysis shows that the constant-temperature model presents the best global description of the Oslo data, closely followed by the mean-field plus combinatorial model and Hartree-Fock plus statistical model. Their accuracies are quite similar, so that it remains difficult to clearly favour one of these models. When considering energies above the threshold where the experimental level scheme is complete, all the six models are shown to lead to rather similar accuracies with respect to Oslo data. The recently proposed shape method can, in principle, improve the situation since it provides an absolute estimate of the excitation-energy dependence of the measured level densities. We show for the specific case of 112 Cd that the shape method could exclude the Hartree-Fock plus statistical model. Such an analysis remains to be performed for the bulk of data for which the shape method can be applied to the Oslo measurements before drawing conclusions on the general quality of a given nuclear level density model.

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