Mass-number and excitation-energy dependence of the spin cutoff parameter

Grimes, S. M.; Voinov, A.; Massey, T. N.

doi:10.1103/physrevc.94.014308

Cited by 17 publications

(12 citation statements)

References 31 publications

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“…( 31) with a factor η, which takes the values η = 0.8, 0.9 and 1.0 for the low, recommended and high values, respectively. Such a systematical error band is consistent with theoretical estimates [87,113,129,118,285]. The usual way to determine the normalization coefficient B of Eq.…”

Section: Brief Overview Of the Standard Oslo Methodssupporting

confidence: 83%

Novel techniques for constraining neutron-capture rates relevant for r-process heavy-element nucleosynthesis

Larsen

Spyrou

Liddick

et al. 2019

Progress in Particle and Nuclear Physics

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The rapid-neutron capture process (r process) is identified as the producer of about 50% of elements heavier than iron.This process requires an astrophysical environment with an extremely high neutron flux over a short amount of time (∼ seconds), creating very neutron-rich nuclei that are subsequently transformed to stable nuclei via β − decay. In 2017, one site for the r process was confirmed: the advanced LIGO and advanced Virgo detectors observed two neutron stars merging, and immediate follow-up measurements of the electromagnetic transients demonstrated an "afterglow" over a broad range of frequencies fully consistent with the expected signal of an r process taking place. Although neutronstar mergers are now known to be r-process element factories, contributions from other sites are still possible, and a comprehensive understanding and description of the r process is still lacking. One key ingredient to large-scale r-process reaction networks is radiative neutron-capture (n, γ) rates, for which there exist virtually no data for extremely neutronrich nuclei involved in the r process. Due to the current status of nuclear-reaction theory and our poor understanding of basic nuclear properties such as level densities and average γ-decay strengths, theoretically estimated (n, γ) rates may vary by orders of magnitude and represent a major source of uncertainty in any nuclear-reaction network calculation of rprocess abundances. In this review, we discuss new approaches to provide information on neutron-capture cross sections and reaction rates relevant to the r process. In particular, we focus on indirect, experimental techniques to measure radiative neutron-capture rates. While direct measurements are not available at present, but could possibly be realized in the future, the indirect approaches present a first step towards constraining neutron-capture rates of importance to the r process.

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Section: Brief Overview Of the Standard Oslo Methodssupporting

confidence: 83%

Novel techniques for constraining neutron-capture rates relevant for r-process heavy-element nucleosynthesis

Larsen

Spyrou

Liddick

et al. 2019

Progress in Particle and Nuclear Physics

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“…( 10) for Θ rigid with η = 0.8, and 0.9 for the low (L) and recommended (R) estimate, respectively. The recommended value is consistent with theoretical estimates of σ J (S n ) in the dysprosium mass region [41][42][43][44][45]. Further, for the upper limit (H), we apply the Hartree-Fock-Bogoliubov-plus-combinatorial (HFB) calculations of Ref.…”

Section: A Renormalization Of Nldssupporting

confidence: 70%

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

et al. 2018

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The photo-neutron cross sections of 162,163 Dy have been measured for the first time in an energy region from the neutron threshold (S n ) up to ≈ 13 MeV. The (γ,n) reaction was induced with quasi-monochromatic laser Compton-scattered γ rays, produced at the NewSUBARU laboratory. The corresponding γ-ray strength functions (γSF) have been calculated from the photo-neutron cross sections. The data are compared to reanalyzed γSFs of 160−164 Dy, which are measured below S n . The excellent agreement with the photo-neutron data at S n confirms the principle of detailed balance. Thus, a complete γSF is established covering in total the energy region of 1 MeV ≤ E γ ≤ 13 MeV. These mid-shell well-deformed dysprosium isotopes all show scissors resonances 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 γSFs.

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“…The level density from the previous step, ρ expt , is now used as the the theoretical level density ρ th in step 1, in lieu of ρ CT . The levels are distributed by spin J, ρ(E * , J) = P (J)ρ(E * ), assuming the Bethe spin-distribution [49], which agrees reasonably well with measurements and more sophisticated calculations [50][51][52], where the probability of a given J is…”

Section: ρ(E * ) Extractionsupporting

confidence: 78%

“…Ref. [51] found roughly a factor of two variability amongst various predictions and experimental constraints for σ 2 in our E * and A region (see also Figure 8). Therefore, we also investigated performing the ρ extraction described in this subsection for a factor of two increase and factor of two decrease in σ 2 .…”

Section: ρ(E * ) Extractionsupporting

confidence: 61%

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Determination of the $^{60}$Zn level density from neutron evaporation spectra

Soltesz,

Mamun,

Voinov

et al. 2021

Preprint

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Nuclear reactions of interest for astrophysics and applications often rely on statistical model calculations for nuclear reaction rates, particularly for nuclei far from β-stability. However, statistical model parameters are often poorly constrained, where experimental constraints are particularly sparse for exotic nuclides. For example, our understanding of the breakout from the NiCu cycle in the astrophysical rp-process is currently limited by uncertainties in the statistical properties of the proton-rich nucleus 60 Zn. We have determined the nuclear level density of 60 Zn using neutron evaporation spectra from 58 Ni( 3 He, n) measured at the Edwards Accelerator Laboratory. We compare our results to a number of theoretical predictions, including phenomenological, microscopic, and shell model based approaches. Notably, we find the 60 Zn level density is somewhat lower than expected for excitation energies populated in the 59 Cu(p, γ) 60 Zn reaction under rp-process conditions. This includes a level density plateau from roughly 5-6 MeV excitation energy, which is counter to the usual expectation of exponential growth and all theoretical predictions that we explore. A determination of the spin-distribution at the relevant excitation energies in 60 Zn is needed to confirm that the Hauser-Feshbach formalism is appropriate for the 59 Cu(p, γ) 60 Zn reaction rate at X-ray burst temperatures.

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Mass-number and excitation-energy dependence of the spin cutoff parameter

Cited by 17 publications

References 31 publications

Novel techniques for constraining neutron-capture rates relevant for r-process heavy-element nucleosynthesis

Novel techniques for constraining neutron-capture rates relevant for r-process heavy-element nucleosynthesis

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

Determination of the $^{60}$Zn level density from neutron evaporation spectra

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