Photoneutron cross sections for samarium isotopes: Toward a unified understanding of (y, n) and (n, y) reactions in the rare earth region

Photoneutron cross sections were measured for the seven stable samarium isotopes Sm-144,Sm-147,Sm-148,Sm-149,Sm-150,Sm-152,Sm-154 near the neutron threshold with quasi-monochromatic laser-Compton scattering gamma rays. Our photoneutron cross sections are found to be low by 20%-37% relative to existing data. The photoneutron data are analyzed with the TALYS reaction code by considering the Skyrme Hartree-Fock-Bogoliubov (HFB) plus quasiparticle random phase approximation (QRPA) model and the axially symmetric deformed Gogny HFB plus QRPA model of the E1 gamma-ray strength. Using the gamma-ray strength function constrained by the present photoneutron data, we made a thorough analysis of the reverse (n,gamma) cross sections including the radioactive nucleus Sm-151 with a half-life of 90 yr. The radiative neutron capture cross section for Sm-153 with the half-life of 1.928 d is deduced with the gamma-ray strength function method

Photoneutron cross sections for neodymium isotopes: Toward a unified understanding of (γ,n) and (n,γ) reactions in the rare earth region

Photoneutron cross sections were measured for five stable Nd isotopes, Nd-143,Nd-144,Nd-145,Nd-146,Nd-148, near neutron threshold with highly monochromatic laser-Compton scattering gamma rays. The photoneutron data were compared with the calculations performed with the TALYS reaction code with inputs of the Skyrme Hartree-Fock-Bogoliubov (HFB) plus quasi-particle random phase approximation (QRPA) model and the axially symmetric deformed Gogny HFB plus QRPA model of E1 gamma-ray strength. Using the gamma-ray strength function constrained by the present photoneutron data, a thorough analysis of the reverse (n, gamma) cross sections is made. Radiative neutron capture cross sections for an s-process branching-point nucleus in the rare earth region, Nd-147 with the half-life 10.98 d, are deduced with the gamma-ray strength function method. The impact of the newly evaluated Nd-147(n, gamma)Nd-148 cross section on s-process nucleosynthesis is discussed

Astrophysical reaction rates and the low-energy enhancement in the gamma-strength

An unexpected enhancement in the γ-strength function for Eγ < 3 MeV for Ti, Sc, V, Fe, and Mo nuclei close to the valley of stability has been discovered at the Oslo Cyclotron Laboratory. Provided that this enhance- ment is present also in very neutron-rich nuclei, it could give an increase in the neutron-capture rates up to two orders of magnitude. However, it is still an open question whether this structure persists when approaching the neutron drip line.info:eu-repo/semantics/publishe

Verification of detailed balance for γ absorption and emission in Dy isotopes

The photoneutron cross sections of 162,163Dy have been measured for the first time in an energy region from the neutron threshold (Sn) up to ≈13MeV. The (γ,n) reaction was induced with quasimonochromatic laser Compton-scattered γ rays, produced at the NewSUBARU laboratory. The corresponding γ -ray strength functions (γ SF) have been calculated from the photoneutron cross sections. The data are compared to reanalyzed γSFs of 160–164Dy, which are measured below Sn. The excellent agreement with the photoneutron data at Sn confirms the principle of detailed balance. Thus, a complete γ SF is established covering in total the energy regionof1 Eγ 13MeV.Thesemid-shellwell-deformeddysprosiumisotopesallshowscissorsresonances with very similar structures. We find that our data predict the same integrated scissors strength as (γ,γ′) data when integrated over the same energy range, which shows that the scissors mode very likely is consistent with the generalized Brink hypothesis. Finally, using the γSFs as input in the reaction code TALYS, we have deduced radiative neutron-capture cross sections and compared them to direct measurements. We find a very good agreement within the uncertainties, which gives further support to the experimentally determined γ SFs

Statistical nuclear properties and synthesis of 138La

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Low-energy enhancement in the γ-ray strength functions of 73,74Ge

The γ -ray strength functions and level densities of 73,74Ge have been extracted up to the neutron-separationenergy Sn from particle-γ coincidence data using the Oslo method. Moreover, the γ -ray strength function of74Ge above Sn has been determined from photoneutron measurements; hence these two experiments cover therange of Eγ≈ 1–13 MeV for 74Ge. The obtained data show that both 73,74Ge display an increase in strength atlow γ energies. The experimental γ -ray strength functions are compared with M1 strength functions deducedfrom average B(M1) values calculated within the shell model for a large number of transitions. The observedlow-energy enhancements in 73,74Ge are adopted in the calculations of the 72,73Ge(n,γ ) cross sections, wherethere are no direct experimental data. Calculated reaction rates for more neutron-rich germanium isotopes areshown to be strongly dependent on the presence of the low-energy enhancement.info:eu-repo/semantics/publishe

First evidence of low energy enhancement in Ge isotopes

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Low-energy enhancement of nuclear gamma strength and its impact on astrophysical reaction rates

An unexpected enhancement in the low-energy part of the gamma-strength function for light and medium-mass nuclei has been discovered at the Oslo Cyclotron Laboratory. This enhancement could lead to an increase in the neutron-capture rates up to two orders of magnitude for very exotic, neutron-rich nuclei. However, it is still an open question whether this structure persists when approaching the neutron drip line.info:eu-repo/semantics/publishe

Low-energy enhancement of nuclear γ strength and its impact on astrophysical reaction rates

An unexpected enhancement in the low-energy part of the γ-strength function for light and medium-mass nuclei has been discovered at the Oslo Cyclotron Laboratory. This enhancement could lead to an increase in the neutron-capture rates up to two orders of magnitude for very exotic, neutron-rich nuclei. However, it is still an open question whether this structure persists when approaching the neutron drip line. © Owned by the authors, published by EDP Sciences, 2014.SCOPUS: cp.pinfo:eu-repo/semantics/publishe