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Postfission properties of uranium isotopes: A hybrid method with Langevin dynamics and the Hauser-Feshbach statistical model
Nuclear Theory · Submitted 18 Jul 2023
abstract compiled · 2026-09-23 · no language-model review
The authors' main claim Conclusions: Our framework is highly reproducible in the experiments and shows that the number of emitted neutrons after fission differs significantly in neutron-rich uranium fission depending on distributions of fission variables.
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Background: Precise understanding of nuclear fission is crucial for experimental and theoretical nuclear physics, astrophysics, and industrial applications; however, the complete physical mechanics is unresolved due to the complexities. Purpose: In this study, we present a new method to describe the dynamical-fission process and following prompt-neutron emission, where we combine the dynamical fission calculation based on the Langevin method and the Hauser-Feshbach statistical model. Methods: Two methods are connected smoothly within the universal charge distribution and the energy conservation, allowing us to calculate a sequence of fission dynamics and post-fission phase, including prompt neutron emission. Results: Using a certain set of model parameters, we successfully reproduce the experimental primary-fission yields, total kinetic energy, independent-fission yields, and prompt neutron emissions for the neutron induced fission of ${}^{236}$U, a compound nucleus of ${\rm n} + {}^{235}{\rm U}$. We elucidate the physical mechanism of the characteristic features observed in previous experiments, such as shell properties. Additionally, we apply our calculation to two very neutron-rich uranium isotopes, i.e., ${}^{250}$U and ${}^{255}$U, which are not experimentally confirmed but are important for r-process nucleosynthesis. Theoretical results indicate that ${}^{250}$U exhibits an asymmetric multiple-peak fission yield distribution, while the neutron-rich ${}^{255}$U has a single peak due to symmetric fission. Our method predicts post-neutron emission fragments, where ${}^{250}$U shows a stronger neutron emissivity than ${}^{255}$U. Conclusions: Our framework is highly reproducible in the experiments and shows that the number of emitted neutrons after fission differs significantly in neutron-rich uranium fission depending on distributions of fission variables.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | Background: Precise understanding of nuclear fission is crucial for experimental and theoretical nuclear physics, astrophysics, and industrial applications; however, the complete physical mechanics is unresolved due to the complexities. | background 1.00 | 0.03 | 0.01 | asserted 1.00 |
| s1 | Purpose: In this study, we present a new method to describe the dynamical-fission process and following prompt-neutron emission, where we combine the dynamical fission calculation based on the Langevin method and the Hauser-Feshbach statistical model. | contribution 1.00 | 0.93 | 0.03 | asserted 0.99 |
| s2 | Methods: Two methods are connected smoothly within the universal charge distribution and the energy conservation, allowing us to calculate a sequence of fission dynamics and post-fission phase, including prompt neutron emission. | method 1.00 | 0.85 | 0.03 | asserted 0.99 |
| s3 | Results: Using a certain set of model parameters, we successfully reproduce the experimental primary-fission yields, total kinetic energy, independent-fission yields, and prompt neutron emissions for the neutron induced fission of ${}^{236}$U, a compound nucleus of ${\rm n} + {}^{235}{\rm U}$. | result 1.00 | 0.96 | 0.12 | asserted 1.00 |
| s4 | We elucidate the physical mechanism of the characteristic features observed in previous experiments, such as shell properties. | interpretation 0.94 | 0.84 | 0.05 | asserted 1.00 |
| s5 | Additionally, we apply our calculation to two very neutron-rich uranium isotopes, i.e., ${}^{250}$U and ${}^{255}$U, which are not experimentally confirmed but are important for r-process nucleosynthesis. | contribution 0.97 | 0.90 | 0.03 | asserted 0.96 |
| s6 | Theoretical results indicate that ${}^{250}$U exhibits an asymmetric multiple-peak fission yield distribution, while the neutron-rich ${}^{255}$U has a single peak due to symmetric fission. | result 1.00 | 0.93 | 0.15 | hedged possibility 0.68 |
| s7 | Our method predicts post-neutron emission fragments, where ${}^{250}$U shows a stronger neutron emissivity than ${}^{255}$U. | result 1.00 | 0.95 | 0.10 | asserted 0.99 |
| s8 | Conclusions: Our framework is highly reproducible in the experiments and shows that the number of emitted neutrons after fission differs significantly in neutron-rich uranium fission depending on distributions of fission variables. | interpretation 0.62 | 0.93 | 0.89 | asserted 1.00 |
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Original abstract
Background: Precise understanding of nuclear fission is crucial for experimental and theoretical nuclear physics, astrophysics, and industrial applications; however, the complete physical mechanics is unresolved due to the complexities. Purpose: In this study, we present a new method to describe the dynamical-fission process and following prompt-neutron emission, where we combine the dynamical fission calculation based on the Langevin method and the Hauser-Feshbach statistical model. Methods: Two methods are connected smoothly within the universal charge distribution and the energy conservation, allowing us to calculate a sequence of fission dynamics and post-fission phase, including prompt neutron emission. Results: Using a certain set of model parameters, we successfully reproduce the experimental primary-fission yields, total kinetic energy, independent-fission yields, and prompt neutron emissions for the neutron induced fission of ${}^{236}$U, a compound nucleus of ${\rm n} + {}^{235}{\rm U}$. We elucidate the physical mechanism of the characteristic features observed in previous experiments, such as shell properties. Additionally, we apply our calculation to two very neutron-rich uranium isotopes, i.e., ${}^{250}$U and ${}^{255}$U, which are not experimentally confirmed but are important for r-process nucleosynthesis. Theoretical results indicate that ${}^{250}$U exhibits an asymmetric multiple-peak fission yield distribution, while the neutron-rich ${}^{255}$U has a single peak due to symmetric fission. Our method predicts post-neutron emission fragments, where ${}^{250}$U shows a stronger neutron emissivity than ${}^{255}$U. Conclusions: Our framework is highly reproducible in the experiments and shows that the number of emitted neutrons after fission differs significantly in neutron-rich uranium fission depending on distributions of fission variables.
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The fission of neutron-rich nuclei is of particular importance in understanding the physics of unstable nuclei and its application to r-process nucleosynthesis, which occurs in neutron-rich astrophysical environments, e.g., in compact-object-binary mergers [ref] (and see recent reviews, e.g, [ref] ).
Actinide-boosting r Process in Black Hole-Neutron Star Merger Ejecta · Introduction · 0.81
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