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arXiv 2024年

作者： Cheng, R.Y. Niu, Y.B. Ma, Y.G. He, W.B. Wang, S.M. Godbey, K. Institute of Modern Physics Fudan University Shanghai200433 China Shanghai Research Center for Theoretical Nuclear Physics NSFC and Fudan University Shanghai200438 China FRIB NSCL Laboratory Michigan State University East LansingMI United States

Recent advances in both theoretical and computational methods have enabled large-scale, precision calculations of the properties of atomic nuclei. With the growing complexity of modern nuclear theory, however, also comes the need for novel methods to perform systematic studies and quantify the uncertainties of models when confronted with experimental data. This study presents an application of such an approach, the reduced basis method, to substantially lower computational costs by constructing a significantly smaller Hamiltonian subspace informed by previous solutions. Our method shows comparable efficiency and accuracy to other dimensionality reduction techniques on an artificial three-body bound system while providing a richer representation of physical information in its projection and training subspace. This methodological advancement can be applied in other contexts and has the potential to greatly improve our ability to systematically explore theoretical models and thus enhance our understanding of the fundamental properties of nuclear systems. Copyright © 2024, The Authors. All rights reserved.

关键词： Hamiltonians

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Nudged elastic band approach to nuclear fission pathways

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Physical Review C 2022年第5期105卷 054302-054302页

作者： Eric Flynn Daniel Lay Sylvester Agbemava Pablo Giuliani Kyle Godbey Witold Nazarewicz Jhilam Sadhukhan Department of Physics and Astronomy and FRIB/NSCL Laboratory Michigan State University East Lansing Michigan 48824 USA FRIB/NSCL Laboratory Michigan State University East Lansing Michigan 48824 USA Department of Statistics and Probability Michigan State University East Lansing Michigan 48824 USA Physics Group Variable Energy Cyclotron Centre Kolkata 700064 India Homi Bhabha National Institute Mumbai 400094 India

关键词： Collective models Fission Isomer decays Lifetimes & widths Nuclear decay Nuclear density functional theory Nuclear many-body theory A ≥ 220

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Effective Description of (formula presented) and the Search for a Narrow (formula presented) Resonance 22nd

Effective Description of (formula presented) and the Search ...

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22nd International Conference on Few-Body Problems in Physics, FB22 2018

作者： Fossez, K. Rotureau, J. Nazarewicz, W. Michel, N. Ploszajczak, M. NSCL/FRIB Laboratory Michigan State University East LansingMI48824 United States Department of Physics and Astronomy and NSCL/FRIB Laboratory Michigan State University East LansingMI48824 United States CEA/DSM - CNRS/IN2P3 BP 55027 Caen Cedex14076 France

ISBN: (纸本)9783030323561

Open quantum systems that are at or beyond the limit of particle-emission stability exhibit generic features stemming from their coupling to an environment of positive energy states and decay channels. In nuclear physics, the exotic helium isotopes (formula presented) and the four-neutron system (formula presented) represent two prototypical cases of open quantum systems whose structures are highly impacted by the environment. In the first part, a practical approach inspired by halo effective field theory for the description of (formula presented) within tens of keV uncertainties is presented and the parity inversion in (formula presented), as well as the possible two-neutron decay of (formula presented) are discussed. The second part discusses the last ab initio results on the four-neutron system obtained using chiral forces and including continuum couplings. © Springer Nature Switzerland AG 2020.

关键词： Neutrons

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Near-Threshold Dipole Strength in Be10 with Isoscalar Character

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Physical Review Letters 2025年第1期134卷 012502-012502页

作者： J. Chen Y. Ayyad D. Bazin W. Mittig M. Z. Serikow N. Keeley S. M. Wang B. Zhou J. C. Zamora College of Science Southern University of Science and Technology Shenzhen 518055 Guangdong China Physics Division Argonne National Laboratory Lemont Illinois 60439 USA IGFAE Universidade de Santiago de Compostela E-15782 Santiago de Compostela Spain FRIB/NSCL Laboratory Michigan State University East Lansing Michigan 48824 USA National Centre for Nuclear Research ulica Andrzeja Sołtana 7 05-400 Otwock Poland Key Laboratory of Nuclear Physics and Ion-beam Application (MOE) Institute of Modern Physics Fudan University Shanghai 200433 China Shanghai Research Center for Theoretical Nuclear Physics NSFC and Fudan University Shanghai 200438 China

Isoscalar dipole transitions are a distinctive fingerprint of cluster structures. A 1− resonance at 7.27(10) MeV, located just below the α-emission threshold, has been observed in the deuteron inelastic scattering reactions off Be10. The deformation lengths of the excited states in Be10 below 9 MeV have been inferred from the differential cross sections using coupled channel calculations. This observed 1− resonance has isoscalar characteristics and exhausts approximately 5%–15% of the isoscalar dipole energy-weighted sum rule, providing evidence for pronounced α cluster structure in Be10. The Gamow coupled channel approach supports this interpretation and suggests the near-threshold effect might be playing an important role in this excitation energy domain. The α+α+n+n four-body calculation reproduces the observed enhanced dipole strength, implying that the four-body cluster structure is essential to describe the 1− states in Be10.

关键词： Inelastic scattering

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Novel evidence for the σ-bond linear-chain molecular structure in ^(14)C

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Chinese Physics C 2021年第8期45卷 71-75页

作者： Han-zhou Yu Jing Li Yan-Lin Ye BiaoYang Cheng-JianLin Hui-Ming Jia Jian-Ling Lou Xiao-Fei Yang T.Baba Qi-Te Li Yu-Cheng Ge Zhi-Huan Li Hui Hua Jin-Yan Xu Zai-Hong Yang Jun Feng Hong-Liang Zang Qiang Liu Wei Jiang Yang Liu Jing-Jing Li Wei Liu Shi-Wei Bai Jie Chen Jia-Xing Han Jia-Hao Chen Kai Ma Dong-Xi Wang Lei Yang Nan-Ru Ma LI-Jie Sun School of Physics and State Key Laboratory of Nuclear Physics and Technology Peking UniversityBeijing 100871China FRIB/NSCL Laboratory Michigan State UniversityEast LansingMichigan 48824USA China Institute of Atomic Energy Beijing 102413China Kitami Institute of Technology 090-8507 KitamiJapan Research Center for Nuclear Physics(RCNP) Osaka University10-1 MihogaokaIbarakiOsaka 567-0047Japan Institute of High Energy Physics Chinese Academy of SciencesBeijing 100049China Spallation Neutron Source Science Center Dongguan 523803China

A multi-nucleon transfer and cluster decay experiment,^(7)Li(^(11)B,^(14)C^(*)→α+^(10)Be)α,is conducted at an incident beam energy of 55 *** reaction channel has a significantly large 0-value,which favors populating the high lying resonant states in ^(14)*** decay paths,from these resonances to various states of the final nucleus ^(10) Be,can be selected,owing to the experimentally achieved optimal resolution of the Q-value spectrum.A number of resonant states are reconstructed from the forward emitting 10Be+α fragments,and their major molecular structures can be detected according to the selective decay paths and relative decay widths.A state at 22.4(2)MeV validates the previously measured and theoretically predicted band head of the positive-parity σ-bond linear-chain mo-lecular *** additional resonances at 22.9(2)and 24.2(2)MeV are identified and consistent with the predicted 2^(+) and 4^(+) members of the same molecular band,thus providing novel evidences for the existence of the exotic clustering chain structure in neutron-rich carbon isotopes.A few high energy resonances,which also indicate the presence of the σ-bond molecular structure,are observed;however,further studies are still required to clarify their ascription in band systematics.

关键词： linear-chain state reaction 0-value transfer reaction cluster decay relative branching ratio

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Coupled-cluster computations of optical potential for medium-mass nuclei

arXiv

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arXiv 2020年

作者： Rotureau, J. NSCL/FRIB Laboratory Michigan State University East LansingMI48824 United States

Recent progress in the numerical solution of the nuclear many-body problem and in the development of nuclear Hamiltonians rooted in Quantum Chromodynamics, has opened the door to first-principle computations of nuclear reactions. In this article, we discuss the current status of ab initio calculations of nucleon-nucleus optical potentials for medium-mass systems, with a focus on results obtained with the coupled-cluster method. Copyright © 2020, The Authors. All rights reserved.

关键词： Nuclear reactions

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Training and Projecting: A Reduced Basis Method Emulator for Many-Body Physics

arXiv

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arXiv 2022年

作者： Bonilla, Edgard Giuliani, Pablo Godbey, Kyle Lee, Dean Department of Physics Stanford University StanfordCA94305 United States FRIB/NSCL Laboratory Michigan State University East LansingMI48824 United States Department of Statistics and Probability Michigan State University East LansingMI48824 United States Department of Physics and Astronomy Michigan State University East LansingMI48824 United States

We present the reduced basis method as a tool for developing emulators for equations with tunable parameters within the context of the nuclear many-body problem. The method uses a basis expansion informed by a set of solutions for a few values of the model parameters and then projects the equations over a well-chosen low-dimensional subspace. We connect some of the results in the eigenvector continuation literature to the formalism of reduced basis methods and show how these methods can be applied to a broad set of problems. As we illustrate, the possible success of the formalism on such problems can be diagnosed beforehand by a principal component analysis. We apply the reduced basis method to the one-dimensional Gross-Pitaevskii equation with a harmonic trapping potential and to nuclear density functional theory for 48Ca, achieving speed-ups of more than x150 in both cases when compared to traditional solvers. The outstanding performance of the approach, together with its straightforward implementation, show promise for its application to the emulation of computationally demanding calculations, including uncertainty quantification. © 2022, CC BY.

关键词： Principal component analysis

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Nudged elastic band approach to nuclear fission pathways

arXiv

引用

arXiv 2022年

作者： Flynn, Eric Lay, Daniel Agbemava, Sylvester Giuliani, Pablo Godbey, Kyle Nazarewicz, Witold Sadhukhan, Jhilam Department of Physics and Astronomy FRIB NSCL Laboratory Michigan State University East LansingMI48824 United States Department of Statistics and Probability Michigan State University East LansingMI48824 United States Physics Group Variable Energy Cyclotron Centre Kolkata700064 India Homi Bhabha National Institute Mumbai400094 India

Background: The nuclear fission process is a dramatic example of the large-amplitude collective motion in which the nucleus undergoes a series of shape changes before splitting into distinct fragments. This motion can be represented by a pathway in the many-dimensional space of collective coordinates. The collective action along the fission pathway determines the spontaneous fission half-lives as well as mass and charge distributions of fission fragments. Purpose: We study the performance and precision of various methods to determine the minimum-action and minimum-energy fission trajectories in the collective space. Methods: We apply the nudged elastic band method (NEB), grid-based methods, and Euler-Lagrange approach to the collective action minimization in two- and three-dimensional collective spaces. Results: The performance of various approaches to the fission pathway problem is assessed by studying the collective motion along both analytic energy surfaces and realistic potential energy surfaces obtained with the Skyrme-Hartree-Fock-Bogoliubov theory. The uniqueness and stability of the solutions is studied. The NEB method is capable of efficient determination of the exit points on the outer turning surface that characterize the most probable fission pathway and constitute the key input for fission studies. This method can also be used to accurately compute the critical points (i.e., local minima and saddle points) on the potential energy surface of the fissioning nucleus that determine the static fission path. The dynamic programming method also performs quite well and it can be used in many-dimensional cases to provide initial conditions for the NEB calculations. Conclusions: The NEB method is the tool of choice for finding the least-action and minimum-energy fission trajectories. It will be particularly useful in large-scale fission calculation of superheavy nuclei and neutron-rich fissioning nuclei contributing to the astrophysical r-process recycling. © 202

关键词： Fission reactions

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Reduced-basis method for few-body bound-state emulation

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Physical Review C 2025年第6期111卷 064315-064315页

作者： R. Y. Cheng (成若玉) K. Godbey Y. B. Niu (牛奕博) W. B. He (何万兵) S. M. Wang (王思敏) Key Laboratory of Nuclear Physics and Ion-beam Application (MOE) Institute of Modern Physics Fudan University Shanghai 200433 China Shanghai Research Center for Theoretical Nuclear Physics NSFC and Fudan University Shanghai 200438 China FRIB/NSCL Laboratory Michigan State University East Lansing Michigan USA

关键词：

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Nuclear level density and γ-decay strength of Sr93

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Physical Review C 2024年第5期109卷 054305-054305页

作者： A. Sweet D. L. Bleuel N. D. Scielzo L. A. Bernstein A. C. Dombos B. L. Goldblum C. M. Harris T. A. Laplace A. C. Larsen R. Lewis S. N. Liddick S. M. Lyons F. Naqvi A. Palmisano-Kyle A. L. Richard M. K. Smith A. Spyrou J. Vujic M. Wiedeking Lawrence Livermore National Laboratory (LLNL) Livermore California 94551 USA Department of Nuclear Engineering University of California Berkeley (UCB) California 94720 USA Lawrence Berkeley National Laboratory (LBNL) Berkeley California 94720 USA Facility for Rare Isotope Beams (FRIB)/National Superconducting Cyclotron Laboratory (NSCL) Michigan State University (MSU) East Lansing Michigan 48824 USA Department of Physics and Astronomy Michigan State University (MSU) East Lansing Michigan 48824 USA Joint Institute for Nuclear Astrophysics (JINA) Michigan State University (MSU) East Lansing Michigan 48824 USA Department of Physics University of Oslo (UiO) N-0316 Oslo Norway Department of Chemistry Michigan State University (MSU) East Lansing Michigan 48824 USA Department of Subatomic Physics iThemba LABS Somerset West 7129 South Africa School of Physics University of the Witwatersrand Johannesburg 2050 South Africa

This work presents the first experimentally determined nuclear level density and γ-ray strength function of the short-lived fission product Sr93, accomplished using the β-Oslo method. Direct measurement of the Sr92(n,γ)Sr93 cross section is not currently possible, as the half-life of 2.66 hours is too short; instead, Sr93 was formed through β decay of Rb93 to excitation energies around the neutron separation energy. The γ-ray spectra were measured using a total absorption spectrometer at the National Superconducting Cyclotron laboratory (nscl) at Michigan State University (MSU). The statistical properties of the Sr93 nucleus were experimentally determined, including the γ-ray strength function and nuclear level density. At low energies, the γ-ray strength function exhibits a constant γ-decay strength, rather than a slightly increasing strength with decreasing γ-ray energy as had been previously observed for several nuclei in this mid-mass region. These statistical properties were then implemented in the reaction code talys1.95 to calculate the Sr92(n,γ)Sr93 cross section.

关键词： Beta decay Energy levels Gamma-ray strength functions Level densities Models & methods for nuclear reactions Nuclear astrophysics Nuclear decay Nuclear reaction rates Nuclear structure & decays Radiative capture 90 ≤ A ≤ 149 Radioactive beams Spectrometers & spectroscopic techniques Thermal & statistical models

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