Nuclear level densities and gamma-ray strength functions of 145,149,151Nd isotopes

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Nuclear level densities and γ -ray strength functions of 180,181Ta and neutron capture cross sections

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Resonances in odd-odd 182Ta

Abstract: Enhanced γ -decay on the tail of the giant electric dipole resonance, such as the scissors or pygmy resonances, can have significant impact on (n,γ ) reaction rates. These rates are important input for modeling processes that take place in astrophysical environments and nuclear reactors. Recent results from the University of Oslo indicate the existence of a significant enhancement in the photon strength function for nuclei in the actinide region due to the scissors resonance. Further, the M1 strength distribution of the scissors resonances in rare earth nuclei has been studied extensively over the years. To investigate the evolution and persistence of the scissor resonance in other mass regions, an experiment was performed utilizing the NaI(Tl) γ -ray detector array (CACTUS) and silicon particle telescopes (SiRi) at the University of Oslo Cyclotron laboratory. Particle-γ coincidences from the 181Ta(d,p)182Ta and 181Ta(d,d’)181Ta reactions were used to measure the nuclear level density and photon strength function of the well-deformed 181Ta and 182Ta systems, to investigate the existence of resonances below the neutron separation energy

gamma-ray strength function for astrophysical applications in the IAEA-CRP

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Excitation energy dependence of prompt fission γ\gamma-ray emission from 241Pu∗^{241}\mathrm{Pu}{}^{*}

International audiencePrompt fission γ rays (PFGs) resulting from the Pu240(d,pf) reaction have been measured as a function of fissioning nucleus excitation energy Ex at the Oslo Cyclotron Laboratory. We study the average total PFG multiplicity per fission, the average total PFG energy released per fission, and the average PFG energy. No significant changes in these characteristics are observed over the range 5.75<Ex<8.25 MeV. The physical implications of this result are discussed. The experimental results are compared to simulations conducted using the computational fission model FREYA. We find that FREYA reproduces the experimental PFG characteristics within 8% deviation across the Ex range studied. Previous excitation energy-dependent PFG measurements conducted below the second-chance fission threshold have large uncertainties, but are generally in agreement with our results within a 2σ confidence interval. However, both a published parametrization of the PFG energy dependence and the most recent PFG evaluation included in ENDF/B-VIII.0 were found to poorly describe the PFG excitation-energy dependence observed in this and previous experiments

γ-Ray Strength Functions and GDR Cross Sections in the IAEA Photonuclear Data Project

We present the latest development of measuring (γ, n) cross sections and giant dipole resonance (GDR) cross sections in the IAEA photonuclear data project. Photoneutron cross sections were measured for 21 isotopes below 2n threshold to construct the γ-ray strength function (γSF) with the γSF method; (γ, n) cross sections are used as experimental constraints on the model E1 and M1 γSFs from the Hartree–Fock–Bogolyubov plus quasi-particle random phase approximation based on the Gogny D1M interaction supplemented with the M1 upbend. GDR cross sections were measured for 11 nuclei from9Be to209Bi by direct neutron-multiplicity sorting with a flat-efficiency neutron detector toward a goal of resolving the long-standing discrepancy between the Livermore and Saclay data. We present γSFs for the Ni isotopic chain and GDR cross sections for159Tb as well as those updated for209Bi.SCOPUS: cp.pinfo:eu-repo/semantics/publishe

Do light nuclei display a universal γ-ray strength function?

In this work we focus on properties in the quasi-continuum of light nuclei. Generally, both level density and γ-ray strength function (γ-SF) differ from nucleus to nucleus. In order to investigate this closer, we have performed particle-γ coincidences using the reactions (p, p'), (p, d) and (p, t) on a 46Ti target. In particular, the very rich data set of the 46Ti(p, p')46Ti inelastic scattering reaction allows analysis of the coincidence data for many independent data sets. Using the Oslo method, we find one common level density for all data sets. If transitions to well-separated low-energy levels are included, the deduced γ-SF may change by a factor of 2 – 3, due strong to Porter-Thomas fluctuations. However, a universal γ-SF with small fluctuations is found provided that only excitation energies above 3 MeV are taken into account. The nuclear structure of the titaniums is discussed within a combinatorial quasi-particle model, showing that only few Nilsson orbitals participate in building up the level density for these light nuclei

Photoneutron cross-section measurements for 165Ho by the direct neutron-multiplicity sorting at Newsubaru

The Coordinated Research Project of the International Atomic Energy Agency (IAEA CRP-F41032) was launched with a goal to publish two compilations of an updated photonuclear data library and a reference database of photon strength functions. The PHOENIX (PHOto-Excitation and Neutron emIssion cross [X] sections) Collaboration has been established for the IAEA-CRP in the γ-ray beam line GACKO (GAmma Collaboration hutch of KOnan university) of the NewSUBARU synchrotron radiation facility in Japan. The collaboration provides (γ, xn) cross-section data to resolveSCOPUS: ar.jinfo:eu-repo/semantics/publishe

Experimentally constrained (p,γ)89Y and (n,γ)89Y reaction rates relevant to p-process nucleosynthesis

The nuclear level density and the γ -ray strength function have been extracted for 89 Y by using the Oslo method on 89Y(p,p′γ)89Y coincidence data. The γ-ray strength function displays a low-energy enhancement consistent with previous observations in this mass region (93–98Mo). Shell-model calculations support the conclusion that the observed enhancement is due to strong, low-energy M1 transitions at high excitation energies. The data were further used as input for calculations of the 88 Sr(p,γ )89 Y and 88 Y(n,γ )89 Y cross sections with the TALYS reaction code. Comparison with cross-section data, where available, as well as with values from the BRUSLIB library, shows a satisfying agreement.info:eu-repo/semantics/publishe