Nuclear mass formula with Bogolyubov-enhanced shell-quenching: application to r-process

Pearson, J. M.; Nayak, R. C.; Goriely, Stéphane

doi:10.1016/0370-2693(96)01071-4

Cited by 208 publications

(202 citation statements)

References 12 publications

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“…In contrast, Hartree-Fock-Bogoliubov (HFB) calculations with the Skyrme force point toward a reduced gap due to a diffused potential caused by the large excess of neutrons [20]. For the r process, some mass models, such as those using HFB with Skyrme force SkP and ETFSI-Q calculations, assuming an N = 82 shell quenching are in better agreement with the abundance distribution around A ≈ 130 [21,22].…”

Section: Introductionmentioning

confidence: 99%

Collectivity evolution in the neutron-rich Pd isotopes toward theN=82shell closure

et al. 2013

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The neutron-rich, even-even 122,124,126 Pd isotopes were studied via in-beam γ -ray spectroscopy at the RIKEN Radioactive Isotope Beam Factory. Excited states at 499(9), 590(11), and 686(17) keV were found in the three isotopes, which we assign to the respective 2 + 1 → 0 + gs decays. In addition, candidates for the 4 + 1 states at 1164(20) and 1300(22) keV were observed in 122 Pd and 124 Pd, respectively. The resulting E x (2 + 1 ) systematics are similar to the Xe (Z = 54) isotopic chain and theoretical predictions by the proton-neutron interacting boson model (IBM-2), indicating the magic nature of N = 82 in the Pd isotopes.

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Section: Introductionmentioning

confidence: 99%

Collectivity evolution in the neutron-rich Pd isotopes toward theN=82shell closure

et al. 2013

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“…As the masses of the extremely neutron-rich nuclei on the rprocess path are not known experimentally, they have to be modeled. For many years, masses derived on the basis of the Finite Range Droplet Model (FRDM) [31] and the ETFSI model (Extended Thomas Fermi Model with Strutinski Integral [32]) have been a standard in r-process simulations. Recently Wang and Liu developed an alternative microscopic-macroscopic mass model (Weizsäcker-Skyrme or WS3 model [33]), which employs a Skyrme energy density formula as a macroscopic basis, which is then microscopically supplemented by shell corrections.…”

Section: Introductionmentioning

confidence: 99%

Nuclear robustness of therprocess in neutron-star mergers

et al. 2015

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We have performed r-process calculations for matter ejected dynamically in neutron star mergers based on a complete set of trajectories from a three-dimensional relativistic smoothed particle hydrodynamic simulation with a total ejected mass of ∼ 1.7 × 10 −3 M . Our calculations consider an extended nuclear network, including spontaneous, β-and neutron-induced fission and adopting fission yield distributions from the ABLA code. In particular we have studied the sensitivity of the r-process abundances to nuclear masses by using different models. Most of the trajectories, corresponding to 90% of the ejected mass, follow a relatively slow expansion allowing for all neutrons to be captured. The resulting abundances are very similar to each other and reproduce the general features of the observed r-process abundance (the second and third peaks, the rare-earth peak and the lead peak) for all mass models as they are mainly determined by the fission yields. We find distinct differences in the predictions of the mass models at and just above the third peak, which can be traced back to different predictions of neutron separation energies for r-process nuclei around neutron number N = 130. In all simulations, we find that the second peak around A ∼ 130 is produced by the fission yields of the material that piles up in nuclei with A 250 due to the substantially longer beta-decay half-lives found in this region. The third peak around A ∼ 195 is generated in a competition between neutron captures and β decays during r-process freeze-out. The remaining trajectories, which contribute 10% by mass to the total integrated abundances, follow such a fast expansion that the r process does not use all the neutrons. This also leads to a larger variation of abundances among trajectories as fission does not dominate the r-process dynamics. The resulting abundances are in between those associated to the r and s processes. The total integrated abundances are dominated by contributions from the slow abundances and hence reproduce the general features of the observed r-process abundances. We find that at timescales of weeks relevant for kilonova light curve calculations, the abundance of actinides is larger than the one of lanthanides. This means that actinides can be even more important than lanthanides to determine the photon opacities under kilonova conditions. Moreover, we confirm that the amount of unused neutrons may be large enough to give rise to another observational signature powered by their decay.

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“…The study of the elemental distribution along the r-process path requires sensitive β-decay related information such as β-decay half-lives, β-delayed neutron-emission probabilities, and nuclear masses. In particular, determination of the timescale that governs matter flow from the r-process "seeds" to the heavy nuclei, as well as the distribution in the r-process peaks, depends sensitively on decay half-lives [1,2].Isotopes with extreme neutron-to-proton ratios in the mass region A = 110 − 125 have attracted special attention since theoretical r-process yields are found to underestimate isotopic abundances observed in the predicted global abundances by an order of magnitude or more [1,3,4]. This discrepancy has been investigated using numerous mass formulae that differ mainly in the strength of the nuclear shell closures [5,6].…”

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confidence: 99%

“…Isotopes with extreme neutron-to-proton ratios in the mass region A = 110 − 125 have attracted special attention since theoretical r-process yields are found to underestimate isotopic abundances observed in the predicted global abundances by an order of magnitude or more [1,3,4]. This discrepancy has been investigated using numerous mass formulae that differ mainly in the strength of the nuclear shell closures [5,6].…”

mentioning

confidence: 99%

β-Decay Half-Lives of Very Neutron-Rich Kr to Tc Isotopes on the Boundary of ther-Process Path: An Indication of Fastr-Matter Flow

et al. 2011

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The β-decay half-lives of 38 neutron-rich isotopes from 36 Kr to 43 Mo and 116,117 Tc are reported here for the first time. These results when compared to previous standard models indicate an overestimation in the predicted half-lives by a factor of two or more in the A ≈ 110 region. A revised model based on the second generation gross theory of β decay better predicts the measured half-lives and suggests a more rapid flow of the rapid neutron-capture process (r-matter flow) through this region than previously predicted.About half of the elements heavier than Fe are thought to be produced in rapid neutron-capture process (rprocess) nucleosynthesis, a sequence of neutron-capture and β-decay processes. Although the astronomical site and the mechanism of the r-process are not yet fully understood, it is generally agreed that the process must occur in environments with extreme neutron densities. The study of the elemental distribution along the r-process path requires sensitive β-decay related information such as β-decay half-lives, β-delayed neutron-emission probabilities, and nuclear masses. In particular, determination of the timescale that governs matter flow from the r-process "seeds" to the heavy nuclei, as well as the distribution in the r-process peaks, depends sensitively on decay half-lives [1,2].Isotopes with extreme neutron-to-proton ratios in the mass region A = 110 − 125 have attracted special attention since theoretical r-process yields are found to underestimate isotopic abundances observed in the predicted global abundances by an order of magnitude or more [1,3,4]. This discrepancy has been investigated using numerous mass formulae that differ mainly in the strength of the nuclear shell closures [5,6]. The results indicate that considerable improvements in the global abundances of the isotopes can be achieved by assuming a quenching of the N = 82 shell gap. The properties of most of these crucial r-process nuclei are, however, currently unknown due to their extremely low production yields in the laboratory.A number of experimental studies on nuclei around neutron-rich krypton to technetium have been performed to investigate the region of the r-process path near N = 82 [7][8][9]. In the current work, we report on a first systematic study of the β-decay properties of very exotic, neutron-rich 36 Kr to 43 Tc nuclides that contribute to the r-process.Decay spectroscopy of very neutron-rich nuclei around A = 110 was performed at the recently-commissioned RIBF facility at RIKEN. A secondary beam, comprised of a cocktail of neutron-rich nuclei, was produced by inflight fission of a 345-MeV/nucleon 238 U beam in a 550-mg/cm 2 Be target. The primary beam was produced by the RIKEN cyclotron accelerator complex with a typical intensity ∼ 0.3 pnA at the production target posi-

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Nuclear mass formula with Bogolyubov-enhanced shell-quenching: application to r-process

Cited by 208 publications

References 12 publications

Collectivity evolution in the neutron-rich Pd isotopes toward theN=82shell closure

Collectivity evolution in the neutron-rich Pd isotopes toward theN=82shell closure

Nuclear robustness of therprocess in neutron-star mergers

β-Decay Half-Lives of Very Neutron-Rich Kr to Tc Isotopes on the Boundary of ther-Process Path: An Indication of Fastr-Matter Flow

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