Tunneling through equivalent multihumped fission barriers: Some implications for the actinide nuclei

Bhandari, B. S.; Alkharam, Ali S

doi:10.1103/physrevc.39.917

Cited by 31 publications

(15 citation statements)

References 31 publications

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“…It was demonstrated in Ref. [36] that the results of recursive calculation agree exactly with those independently obtained for transmission through real potentials by Martinelli et al [43] and Bhandari [44,45], as well as with the transmission coefficients through a triple-humped barrier that consider absorption in the second well [33].…”

Section: Triple-humped Barriersupporting

confidence: 75%

Extended optical model for fission

et al. 2016

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A comprehensive formalism to calculate fission cross sections based on the extension of the optical model for fission is presented. It can be used for description of nuclear reactions on actinides featuring multi-humped fission barriers with partial absorption in the wells and direct transmission through discrete and continuum fission channels. The formalism describes the gross fluctuations observed in the fission probability due to vibrational resonances, and can be easily implemented in existing statistical reaction model codes. The extended optical model for fission is applied for neutron induced fission cross-section calculations on 234,235,238 U and 239 Pu targets. A triple-humped fission barrier is used for 234,235 U(n,f ), while a double-humped fission barrier is used for 238 U(n,f ) and 239 Pu(n,f ) reactions as predicted by theoretical barrier calculations. The impact of partial damping of class-II/III states, and of direct transmission through discrete and continuum fission channels, is shown to be critical for a proper description of the measured fission cross sections for 234,235,238 U(n,f ) reactions. The 239 Pu(n,f ) reaction can be calculated in the complete damping approximation. Calculated cross sections for 235,238 U(n,f ) and 239 Pu(n,f ) reactions agree within 3% with the corresponding cross sections derived within the Neutron Standards least-squares fit of available experimental data. The extended optical model for fission can be used for both theoretical fission studies and nuclear data evaluation.

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Section: Triple-humped Barriersupporting

confidence: 75%

Extended optical model for fission

et al. 2016

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“…Macroscopic-microscopic model calculations predicted, already in the 1970s [5][6][7], the occurrence of shallow third minima beyond the second barrier. These minima were used to explain the thorium anomaly [6][7][8]. High resolution fission cross section * sgzhou@itp.ac.cn measurements for 230−233 Th and 237 U supported the existence of shallow third minima on the PES's of these nuclei [9][10][11][12][13][14][15].…”

Section: Introductionmentioning

confidence: 99%

Multidimensionally constrained relativistic mean-field study of triple-humped barriers in actinides

et al. 2015

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Background: Potential energy surfaces (PES's) of actinide nuclei are characterized by a two-humped barrier structure. At large deformations beyond the second barrier, the occurrence of a third barrier was predicted by macroscopic-microscopic model calculations in the 1970s, but contradictory results were later reported by a number of studies that used different methods. Purpose: Triple-humped barriers in actinide nuclei are investigated in the framework of covariant density functional theory (CDFT). Methods: Calculations are performed using the multidimensionally constrained relativistic mean field (MDC-RMF) model, with the nonlinear point-coupling functional PC-PK1 and the density-dependent meson exchange functional DD-ME2 in the particle-hole channel. Pairing correlations are treated in the BCS approximation with a separable pairing force of finite range. Results: Two-dimensional PES's of 226.228.230,232 ancj 2 3 2 .2 3 4 .2 3 6 .2 3 8 y are mappe(i and the third minima on these surfaces are located. Then one-dimensional potential energy curves along the fission path are analyzed in detail and the energies of the second barrier, the third minimum, and the third barrier are determined. The functional DD-ME2 predicts the occurrence of a third barrier in all Th nuclei and 238U. The third minima in 230.2327}, are very shallow, whereas those in 226.2287}, and 238U are quite prominent. With the functional PC-PK1 a third barrier is found only in 226 .2 2 8 .2 3 0 7 }, single-nucleon levels around the Fermi surface are analyzed in 226Th, and it is found that the formation of the third minimum is mainly due to the Z = 90 proton energy gap at f 2o ~ 1 -5 and fto » 0.7. Conclusions: The possible occurrence of a third barrier on the PES's of actinide nuclei depends on the effective interaction used in multidimensional CDFT calculations. More pronounced minima are predicted by the DD-ME2 functional, as compared to the functional PC-PK1. The depth of the third well in Th isotopes decreases with increasing neutron number. The origin of the third minimum is due to the proton Z = 90 shell gap at relevant deformations.

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“…For 228 Th, the third potential well becomes shallower and the depth predicted from MDC-RMF calculations with PC-PK1 (DD-ME2) is 0.78 (1.13) MeV. The third minimum is the most pronounced in 226,228 Th among the nuclei considered in Ref. [133].…”

Section: One-dimensional Pecs Around the Third Minimum And The Third mentioning

confidence: 96%

“…We investigated even-even Th and U isotopes, namely, 226,228,230,232 Th and 232,234,236,238 U. In Fig.…”

Section: Two-dimensional Pes's Beyond the Second Fission Barriermentioning

confidence: 99%

Multidimensionally constrained covariant density functional theories—nuclear shapes and potential energy surfaces

Zhou

2016

Phys. Scr.

120

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The intrinsic nuclear shapes deviating from a sphere not only manifest themselves in nuclear collective states but also play important roles in determining nuclear potential energy surfaces (PES's) and fission barriers. In order to describe microscopically and selfconsistently nuclear shapes and PES's with as many shape degrees of freedom as possible included, we developed multidimensionallyconstrained covariant density functional theories (MDC-CDFTs). In MDC-CDFTs, the axial symmetry and the reflection symmetry are both broken and all deformations characterized by β λµ with even µ are considered. We have used the MDC-CDFTs to study PES's and fission barriers of actinides, the non-axial octupole Y 32 correlations in N = 150 isotones and shapes of hypernuclei. In this Review we will give briefly the formalism of MDC-CDFTs and present the applications to normal nuclei. arXiv:1605.00956v2 [nucl-th]

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Tunneling through equivalent multihumped fission barriers: Some implications for the actinide nuclei

Cited by 31 publications

References 31 publications

Extended optical model for fission

Extended optical model for fission

Multidimensionally constrained relativistic mean-field study of triple-humped barriers in actinides

Multidimensionally constrained covariant density functional theories—nuclear shapes and potential energy surfaces

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