Bulletin of the American Physical Society
6th Joint Meeting of the APS Division of Nuclear Physics and the Physical Society of Japan
Sunday–Friday, November 26–December 1 2023; Hawaii, the Big Island
Session F11: Minisymposium: Accessing the Third r-Process Peak: Nuclear Structure and Fission Studies |
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Chair: Maxime Brodeur, University of Notre Dame Room: Hilton Waikoloa Village Kings 1 |
Thursday, November 30, 2023 9:00AM - 9:30AM |
F11.00001: Study of the single-neutron excitation of 207Hg and the fission barrier of 289U using solenoidal spectrometers Invited Speaker: Tsz Leung Tang Experimental knowledge of the basic nuclear properties of nuclei south and east of 208Pb remains elusive. These nuclei have hitherto been challenging to produce, yet playing a crucial role in understanding the third r-process peak. Properties such as mass, decay rates, and single-particle levels, play a crucial role in evolving our understanding of the third r-process peak. Fission has also been postulated to play a crucial role. At present, theoretical models outpace experimental data, yet the latter is crucial to help benchmark these models. In this talk, I highlight new experimental approaches to elucidate information on single-particle and fission properties of nuclei relevant to the third r-process peak, centered on the solenoidal spectrometer technique [1]. A trio of solenoidal spectrometers has been established to capitalize on the availability of exotic beams at Argonne (HELIOS), FRIB (SOLARIS), and ISODLE (the ISS). I will showcase two recent, successful demonstrations utilizing this approach. The first focuses on the extraction of neutron-single-particle energies for 207Hg [2], while the second highlights the determination of the fission barrier for 239U [3]. |
Thursday, November 30, 2023 9:30AM - 9:45AM |
F11.00002: An application of shell model to low-energy induced fission Kouichi Hagino, George F Bertsch One of the most challenging problems in nuclear physics is to describe |
Thursday, November 30, 2023 9:45AM - 10:00AM |
F11.00003: Microscopic description of induced fission in a configuration-interaction approach Kotaro Uzawa, Koichi Hagino Since the discovery of nuclear fission, many phenomenological models have been proposed and have successfully explained the observed behaviors. |
Thursday, November 30, 2023 10:00AM - 10:15AM |
F11.00004: Accessing the last r-process abundance peak at the N=126 Factory through high precision mass measurements Biying Liu, Maxime Brodeur, Jason A Clark, Alicen M Houff, Russell A Knaack, Matthew R Mumpower, William S Porter, Fabio Rivero, John Rohrer, Guy Savard, Kumar S Sharma, Adrian A Valverde, Bruce J Zabransky, Regan Zite The rapid neutron capture process (r-process) is responsible for the production of almost half of the natural elements heavier than iron. In order to obtain reliable calculations of r-process abundances for the models of neutron star merger and other potential astrophysical sites, precise and accurate information about neutron-rich isotopes, including their masses, is needed. In order to access the neutron-rich nuclei around the N=126 region to study the last and least explored r-process abundance peak, the future N=126 Factory is under construction at Argonne National Laboratory (ANL). The N=126 Factory uses multi-nucleon transfer reactions to produce neutron-rich nuclei coming out close to the grazing angle. The products can be efficiently collected, separated and delivered to experiments for further study with the beam manipulation techniques developed for CARIBU, using the gas catcher, magnetic separator, RFQ cooler-buncher and Notre Dame multi-reflection time-of-flight mass spectrometer (MR-TOF). |
Thursday, November 30, 2023 10:15AM - 10:30AM |
F11.00005: Beta-delayed neutron measurements of neutron-rich nuclei near N = 126 at RIBF Tik Tsun Yeung, Shunji Nishimura, Vi H Phong, Anabel Morales, Jin Wu, Tadaaki Isobe, Megumi Niikura, Hiroyoshi Sakurai, Tom Davinson, Iris Dillmann, Alfredo Estrade, Naoki Fukuda, Robert Grzywacz, Oscar Hall, Yoshikazu Hirayama, Eiji Ideguchi, Kei Kokubun, Filip G Kondev, Rurie Mizuno, Momo Mukai, Neerajan Nepal, Mohamad Nor Nurhafiza, Krzysztof Piotr P Rykaczewski, Lewis Sexton, Jose L Tain, Yutaka X Watanabe, Rin Yokoyama The neutron-rich N ~ 126 region is important to r-process calculation around the third abundance peak and study of shell evolution across N = 126 shell closure. However, only limited information about their nuclear properties is available. Experimental measurements of nuclear properties of more exotic nuclei are essential to verify theoretical models [1,2]. |
Thursday, November 30, 2023 10:30AM - 10:45AM |
F11.00006: Post-fission properties of uranium isotopes: a hybrid method with Langevin dynamics and the Hauser-Feshbach statistical model Shoya Tanaka, Nobuya Nishimura, Futoshi Minato, Yoshihiro Aritomo In this study, we present a new method to describe the dynamical fission process and following prompt-neutron emission, where the fission calculation based on the Langevin method and the Hauser-Feshbach statistical model are combined. 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. Using a certain set of model parameters, we successfully reproduce experimental fission-fragment distributions, total kinetic energy, and prompt neutron emissions for the neutron induced fission of 235U. Additionally, we apply our calculation to two very neutron-rich uranium isotopes, i.e., 250U and 255U, which are not experimentally confirmed, but are relevant to r-process nucleosynthesis. Our method successfully predicts post-neutron emission fragment distributions, where 250U shows a stronger neutron emissivity than 255U. The predictions of the calculations, which are highly reproducible in the experiments, show that not only the distribution of fission variables but also the number of neutron emissions differ significantly in neutron-rich uranium fission. |
Thursday, November 30, 2023 10:45AM - 11:00AM |
F11.00007: Production and Discovery of Neutron Rich Isotopes by Fragmentation of 198Pt Kenny Haak, Oleg B Tarasov, Partha Chowdhury, Andrew M Rogers, Kartikeya Sharma, Thomas Baumann, Daniel Bazin, Peter C Bender, Jun Chen, Alfredo Estrade, Michael A Famiano, Dan C Foulds-Holt, Naoki Fukuda, Alexandra Gade, Tom N Ginter, Richard W Gohier, Marc Hausmann, Ava Hill, Daniel E Hoff, Levi Klankowski, Elaine Kwan, Jingyi Li, Sean N Liddick, Brenden R Longfellow, Stephanie M Lyons, Chris Morse, Mauricio Portillo, Daniel Rhodes, Andrea Richard, Sithira Samaranayake, Bradley M Sherrill, Mark Spieker, Chandana S Sumithrarachchi, Hiroshi Suzuki, Kailong Wang, Sanjanee W Waniganeththi, Dirk W Weisshaar, Shaofei Zhu The properties of neutron-rich heavy isotopes near the N = 126 shell closure are important for our understanding of nuclear physics and play a fundamental role in astrophysical processes such as the r-process. Despite their importance, the N = 126 isotones for atomic numbers less than lead are poorly studied due to the lack of sufficiently high production cross sections. In order to establish a footing in this region and eventually reach out toward the location of the r-process pathway and beyond, it is desirable to perform experiments studying the production of neutron rich isotopes in the Hf-Pt region. |
Thursday, November 30, 2023 11:00AM - 11:15AM |
F11.00008: Abstract Withdrawn
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Thursday, November 30, 2023 11:15AM - 11:30AM |
F11.00009: Proposed measurements for potential astromers Matthew R Mumpower, Wendell Misch, Trevor M Sprouse Astrophysically metastable nuclear isomers (astromers) may significantly impact the creaton of the elements. Astromers can accelerate or delay energy release, influence electromagnetic signals and alter pathways during nucleosynthesis. We report on the present knowledge of astromers for several astrophysical nucleosynthesis processes. We isolate unmeasured nuclear properties that may be measured at experimental facilities. Future theoretical and experimental endeavors will help to resolve the role of these excited states in astrophysical plasmas. |
Thursday, November 30, 2023 11:30AM - 11:45AM |
F11.00010: Isomer Decay Spectroscopy of Neutron-Rich Nuclei beyond N=126 Shell Closure Jin Wu, Anabel Morales, Tik Tsun Yeung, Shunji Nishimura, Naoki Fukuda, Jose L Tain, Tom Davinson, Oscar Hall, Vi Ho Phong, Lewis Sexton, Zs Podolyak, Hiroyoshi Sakurai, Phil Woods The region south of the heaviest double magic nuclei 208Pb, acting as a gateway past N = 126 shell closure that strongly affects the synthesis of heaviest elements during the merger of neutron stars [1], suffers from a severe lack of experimental data, with the current level scheme of 204Pt being the last N = 126 isotope only four neutrons away removed from Z = 82. A new opportunity to study nuclear shell and shape evolution in neutron-rich nuclei relevant to the r-process nucleosynthesis emerged from the beta-decay spectroscopy in the vicinity of the N = 126 closed shell. This contribution will focus on the preliminary results of isomeric states in the “southeast” of doubly-magic nucleus 208Pb identified in an experiment carried out in the “BRIKEN” decay-spectroscopy campaign at the RIBF facility, RIKEN [2]. The selected level schemes will be interpreted in terms of the shell model calculations. Future perspectives of contentiously exploring seniority schemes and shape evolution in this region will also be discussed. |
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