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Title: Assessing theoretical uncertainties in fission barriers of superheavy nuclei

Abstract

Here, theoretical uncertainties in the predictions of inner fission barrier heights in superheavy elements have been investigated in a systematic way for a set of state-of-the-art covariant energy density functionals which represent major classes of the functionals used in covariant density functional theory. They differ in basic model assumptions and fitting protocols. Both systematic and statistical uncertainties have been quantified where the former turn out to be larger. Systematic uncertainties are substantial in superheavy elements and their behavior as a function of proton and neutron numbers contains a large random component. The benchmarking of the functionals to the experimental data on fission barriers in the actinides allows to reduce the systematic theoretical uncertainties for the inner fission barriers of unknown superheavy elements. However, even then they on average increase on moving away from the region where benchmarking has been performed. In addition, a comparison with the results of non-relativistic approaches is performed in order to define full systematic theoretical uncertainties over the state-of-the-art models. Even for the models benchmarked in the actinides, the difference in the inner fission barrier height of some superheavy elements reaches $5-6$ MeV. This uncertainty in the fission barrier heights will translate into huge (many tensmore » of the orders of magnitude) uncertainties in the spontaneous fission half-lives.« less

Authors:
 [1];  [1];  [1];  [2]
  1. Mississippi State Univ., Mississippi State, MS (United States)
  2. Technische Univ. Munchen, Garching (Germany)
Publication Date:
Research Org.:
Mississippi State Univ., Mississippi State, MS (United States)
Sponsoring Org.:
USDOE National Nuclear Security Administration (NNSA); USDOE Office of Science (SC), Nuclear Physics (NP) (SC-26)
OSTI Identifier:
1356774
Grant/Contract Number:
NA0002925; SC0013037
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Physical Review C
Additional Journal Information:
Journal Volume: 95; Journal Issue: 5; Journal ID: ISSN 2469-9985
Publisher:
American Physical Society (APS)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY

Citation Formats

Agbemava, S. E., Afanasjev, A. V., Ray, D., and Ring, P. Assessing theoretical uncertainties in fission barriers of superheavy nuclei. United States: N. p., 2017. Web. doi:10.1103/PhysRevC.95.054324.
Agbemava, S. E., Afanasjev, A. V., Ray, D., & Ring, P. Assessing theoretical uncertainties in fission barriers of superheavy nuclei. United States. doi:10.1103/PhysRevC.95.054324.
Agbemava, S. E., Afanasjev, A. V., Ray, D., and Ring, P. 2017. "Assessing theoretical uncertainties in fission barriers of superheavy nuclei". United States. doi:10.1103/PhysRevC.95.054324.
@article{osti_1356774,
title = {Assessing theoretical uncertainties in fission barriers of superheavy nuclei},
author = {Agbemava, S. E. and Afanasjev, A. V. and Ray, D. and Ring, P.},
abstractNote = {Here, theoretical uncertainties in the predictions of inner fission barrier heights in superheavy elements have been investigated in a systematic way for a set of state-of-the-art covariant energy density functionals which represent major classes of the functionals used in covariant density functional theory. They differ in basic model assumptions and fitting protocols. Both systematic and statistical uncertainties have been quantified where the former turn out to be larger. Systematic uncertainties are substantial in superheavy elements and their behavior as a function of proton and neutron numbers contains a large random component. The benchmarking of the functionals to the experimental data on fission barriers in the actinides allows to reduce the systematic theoretical uncertainties for the inner fission barriers of unknown superheavy elements. However, even then they on average increase on moving away from the region where benchmarking has been performed. In addition, a comparison with the results of non-relativistic approaches is performed in order to define full systematic theoretical uncertainties over the state-of-the-art models. Even for the models benchmarked in the actinides, the difference in the inner fission barrier height of some superheavy elements reaches $5-6$ MeV. This uncertainty in the fission barrier heights will translate into huge (many tens of the orders of magnitude) uncertainties in the spontaneous fission half-lives.},
doi = {10.1103/PhysRevC.95.054324},
journal = {Physical Review C},
number = 5,
volume = 95,
place = {United States},
year = 2017,
month = 5
}

Journal Article:
Free Publicly Available Full Text
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  • The dependence of fission barriers on the excitation energy of the compound nucleus impacts the survival probability of superheavy nuclei synthesized in heavy-ion fusion reactions. We study the temperature-dependent fission barriers by means of the self-consistent nuclear density functional theory. The equivalence of isothermal and isentropic descriptions is demonstrated. The effect of the particle gas is found to be negligible in the range of temperatures studied. Calculations have been carried out for ^{264}Fm, ^{272}Ds, ^{278}112, ^{292}114, and ^{312}124. For nuclei around ^{278}112 produced in "cold fusion" reactions, we predict a more rapid decrease of fission barriers with temperature as comparedmore » to the nuclei around ^{292}114 synthesized in "hot fusion" experiments. This is explained in terms of the difference between the ground-state and fission-barrier temperatures. Our calculations are consistent with the long survival probabilities of the superheavy elements produced in Dubna with the ^{48}Ca beam.« less
  • A systematic study of fission-barrier dependence on excitation energy has been performed using the self-consistent finite-temperature Hartree-Fock+BCS (FT-HF+BCS) formalism with the SkM* Skyrme energy density functional. The calculations have been carried out for even-even superheavy nuclei with Z ranging between 110 and 124. For an accurate description of fission pathways, the effects of triaxial and reflection asymmetric degrees of freedom have been fully incorporated. Our survey demonstrates that the dependence of isentropic fission barriers on excitation energy changes rapidly with particle number, pointing to the importance of shell effects even at large excitation energies characteristic of compound nuclei. The fastestmore » decrease of fission barriers with excitation energy is predicted for deformed nuclei around N = 164 and spherical nuclei around N = 184 that are strongly stabilized by ground-state shell effects. For nuclei ^{240}Pu and ^{256}Fm, which exhibit asymmetric spontaneous fission, our calculations predict a transition to symmetric fission at high excitation energies due to the thermal quenching of static reflection asymmetric deformations.« less
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