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 L10: Nuclear Structure V |
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Chair: Nori Aoi Room: Hilton Waikoloa Village Kohala 3 |
Friday, December 1, 2023 9:00AM - 9:15AM |
L10.00001: Precision Spectroscopy of Fast, Hot Exotic Isotopes for Nuclear Structure Silviu-Marian Udrescu Collinear resonant ionization laser spectroscopy has been for a long time an important tool for studying the properties of short-lived nuclei away from stability such as nuclear spins, electromagnetic moments and changes in the nuclear root-mean-square charge radii. In order to achieve high efficiency and precision, the ion beams used for such studies are often cooled down and bunched in gas filled radio-frequency ion traps. However, this approach is unsuitable for many species of interest, such as highly reactive ones or those with lifetime shorter (<5 ms) than the trapping time. In this contribution, I will present the developments of a highly sensitive experimental scheme to enable high-precision laser spectroscopy studies of such short-lived isotopes, produced in hot environments, without the need for cooling techniques. |
Friday, December 1, 2023 9:15AM - 9:30AM |
L10.00002: First results from ATLANTIS - A new collinear laser spectroscopy setup at Argonne National Laboratory Bernhard Maass, Alex J Brinson, Daniel Burdette, Jason A Clark, Adam J Dockery, Max Horst, Phillip Imgram, Kristian König, Kei Minamisono, Patrick Müller, Peter Mueller, Wilfried Nörtershäuser, Skyy V Pineda, Simon Rausch, Laura Renth, Brooke J Rickey, Daniel Santiago-Gonzalez, Guy Savard, Felix Sommer, Adrian A Valverde Neutron-rich nuclei of refractory metals below the magic number Z=50 exhibit rich phenomena such as deformation, shape coexistence, and hints of triaxiality and thus are ideal testing grounds for theories describing these collective properties. Laser spectroscopy of isotopes and isomers in this region can contribute valuable and complementary data with high precision on nuclear shapes, sizes, and electromagnetic moments. |
Friday, December 1, 2023 9:30AM - 9:45AM |
L10.00003: Simulations of Neutron Unbound Physics for Geant4 Nicholas Mendez, Thomas Baumann, Paul Gueye The study of neutron unbound systems via the invariant mass technique is the primary focus of the MoNA Collaboration, which built and operates the Modular Neutron Array (MoNA) and the Large multi-Institutional Scintillator Array (LISA) at FRIB. Advancements in nuclear structure from theory and experiment along the neutron dripline have presented opportunities to understand the nature of unbound systems in higher mass nuclei. The GEometry And Tracking (Geant4) platform has been used in high-energy and nuclear physics to simulate particle interaction with as much detail as the user desires. Geant4 currently does not have a physics class to simulate neutron unbound systems. Given the advancement of accelerator facilities and active searches along the neutron dripline, detailed simulations to study the breakup of neutron unbound systems, are necessary. [MN1] The implementation of the breakup of neutron unbound systems in Geant4 will be presented. |
Friday, December 1, 2023 9:45AM - 10:00AM |
L10.00004: Extraction of the Nuclear Level Density 68Cu and 65Ni using LANSCE/WNR neutron beams and the evaporation technique Nikolaos Dimitrakopoulos, Georgios Perdikakis, Panagiotis Gastis, Alexander Voinov, Sean A Kuvin, Pelagia Tsintari, Hye Young Lee, Honey Arora Nuclear reactions involved in stellar evolution generally occur at energies much lower than the Coulomb barrier, making neutron induced reactions vital in the synthesis of chemical elements, particularly those heavier than iron. Reactions of the (n,a) and (n,p) types can be utilized to extract nuclear level densities (NLD) of unstable isotopes, essential for accurate reaction rate calculations, using the evaporation technique. To probe nuclear level densities in the Ni region, cross sections measurements for 68Zn(n,p)68Cu and 68Zn(n,a)65Ni were carried out at WNR facility at LANSCE using the Low Energy (n,z) (LENZ) detection system. |
Friday, December 1, 2023 10:00AM - 10:15AM |
L10.00005: Search for Shape Coexistence Signatures in 100Ru using Thermal Neutron Capture Reaction Sangeet-Pal S Pannu, Paul E Garrett, Vinzenz Bildstein, Marco Rocchini, Giacomo Columbi, Caterina Michelagnoli, Kim H Yung, Katharina Ide, Maike Beuschlein, Kevin Ortner, Javier R Murias, Jason Froats, Costel Petrache, Norbert Pietralla Recent studies within the Zr (Z=40) - Sn (Z=50) region have shown several nuclei to possess shape coexistence which occurs when states existing in a narrow energy gap within the same nucleus possess distinct shapes. In the Ru (Z=44) isotopes, strong evidence has emerged for shape coexistence within 102Ru and 104Ru from Coulomb excitation [1,2], and it was suggested in 98Ru and 100Ru as well [3]. In order to explore shape coexistence in 100Ru, and also probe possible vibrational motion, key mixing ratios and the observation of low-energy, and hence often very weak intensity, transitions between non-yrast states are required. This study of 100Ru presented in this work aims to extract precise mixing ratios, unobserved weak g-ray transitions and transition probabilities to resolve its structural behaviour. We used the thermal neutron capture reaction, 99Ru(n,g)100Ru, carried out at the Institut Laue-Langevin in Grenoble, France [4]. The g-ray transitions depopulating the excited states in 100Ru were detected by the FIPPS array consisting of two sets of eight clover-type hyper-pure Germanium detectors. A total of 106 combined angle pairs permitted precise g-g angular correlations analysis. Preliminary results from the current analysis will be presented with emphasis on the mixing ratios of the g-ray transitions. |
Friday, December 1, 2023 10:15AM - 10:30AM |
L10.00006: Beta-decay study of the shape coexistence in 98Zr Konstantin R Mashtakov, Paul E Garrett, Bruno Olaizola, Corrina Andreoiu, Gordon C Ball, Peter C Bender, Vinzenz Bildstein, David S Cross, Hillary Dawkins, Greg A Demand, A. Diaz Varela, Gatjang Deng, Adam B Garnsworthy, Greg Hackman, Baharak Hadinia, Alex T Laffoley, Mohamad Moukaddam, Jason Park, Erin E Peters, Allison J Radich, Mustafa M Rajabali, Evan T Rand, Usman Rizwan, Balraj Singh, Krzysztof Starosta, Carl E Svensson, Philip J Voss, Z.-M. Wang, John L Wood, Steven W Yates, Aaron Chester Anomalies in the systematics of nuclear properties challenge our understanding of the underlying nuclear structure. One such anomaly emerges in the Zr isotopic chain as a dramatic ground-state shape change, abruptly shifting from spherical into a deformed one at N=60. This research focuses on 98Zr which lies on the interface between spherical and deformed phases. While past research provided an over-all understanding of 98Zr's nuclear structure [1,2,3,4,5], most recent studies employing state-of-the-art theoretical models presented conflicting interpretations of its higher-lying bands [6,7].
A β-decay experiment was conducted at the TRIUMF-ISAC facility utilizing the 8π spectrometer to resolve these uncertainties. The obtained data allowed the determination of branching ratios for weak transitions, crucial for assigning band structures. Observing the key 155-keV 22+ → 03+ transition enabled the determination of its B(E2) value for the first time. Additionally, γ-γ angular correlation measurements allowed us to establish the 0+, 2+, and I = 1 natures for multiple newly observed and previously known (but not firmly assigned) states as well as mixing ratios. The new results revealed the collective character of certain key transitions, supporting the multiple shape coexistence interpretation provided by the framework of Monte Carlo Shell Model (MCSM). These results will be presented and discussed in relation to both MCSM and Interacting Boson Model with configuration mixing calculations.
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Friday, December 1, 2023 10:30AM - 10:45AM |
L10.00007: Studies of the N=60 shape transition; states in 98Sr populated via β-decay Paul E Garrett, Konstantin R Mashtakov, Fatima Aljarrah, Corina Andreoiu, Gordon C Ball, Peter C Bender, Vinzenz Bildstein, Aaron Chester, David S Cross, Hillary Dawkins, Greg A Demand, Gatjang Deng, A. Diaz Varela, Adam B Garnsworthy, Greg Hackman, Baharak Hadinia, Alex T Laffoley, Mohamad Moukaddam, Bruno Olaizola, Jason Park, Erin E Peters, Mustafa M Rajabali, Allison J Radich, Evan T Rand, Balraj Singh, Krzysztof Starosta, Carl E Svensson, Usman Rizwan, Z.-M. Wang, Steven W Yates, John L Wood The evolution of ground-state shapes usually proceeds smoothly, however for Sr and Zr nuclei at N=60 there is an abrupt shape transition. The dramatic onset of deformation in 100Zr was recently well reproduced in state-of-the-art Monte Carlo Shell Model calculations [1], which also predict that the same deformed configuration may coexist at higher excitation energies in the lighter Zr isotopes. The excited state spectrum of 98Sr possesses very low-lying 21+ and 02+ states, just as in 100Zr (see, e.g., Ref. [2]). Unfortunately, information on higher-lying configurations in 98Sr is sparse, and, for example, there are no firmly assigned 0+ states above the 02+ level. In an experiment at the TRIUMF-ISAC facility, we have studied the β-decay of 98Rb to 98Sr. The high-statistics of the data obtained permitted the determination of branching ratios for very weak transitions important for assigning band structures. Additionally, γ-γ angular correlation measurements were used for both spin assignments and mixing ratios. Firm spin assignments have been made for additional excited 0+ and 2+ states, with the 03+ band suggested up to spin 4. These results will be placed in the context of the systematics [2] in the Sr isotopes, and the similarities in the structures of 98Sr and 100Zr will be discussed. |
Friday, December 1, 2023 10:45AM - 11:00AM |
L10.00008: Structure of beta-decaying isomers in deformed, odd-odd 102,104Nb nuclei* Filip G Kondev, Soumen Nandi, Michael P Carpenter, Jason A Clark, Patrick A Copp, Daryl J Hartley, Heshani Jayatissa, Torben Lauritsen, Scott T Marley, Graeme Morgan, Gopal Mucharjee, Claus Mueller Gatermann, Walter Reviol, Daniel Santiago-Gonzalez, Guy Savard, Dariusz Seweryniak, Jin Wu Properties of neutron-rich nuclei in the A~100 mass region are important for achieving better understanding of the nuclear structure where the knowledge is limited due to difficulties in the production of these nuclei with high purity and intensity. They are an essential ingredient in the interpretation of the r-process nucleosynthesis and are needed in fission-like applications which depend sensitively on the nuclear structure data input. |
Friday, December 1, 2023 11:00AM - 11:15AM |
L10.00009: New Results on 134Te From 134Sb β-Decay Graeme Morgan, Scott T Marley, Patrick A Copp, Michael P Carpenter, Partha Chowdhury, Daryl J Hartley, Heshani Jayatissa, Kay Kolos, Filip G Kondev, Sergio Lopez-Caceres, A.J. Mitchell, Soumen Nandi, Walter Reviol, Andrew M Rogers, Dariusz Seweryniak, Rachel M Shaffer, Barbara S Wang, Sanjanee W Waniganeththi, Gemma L Wilson, Sudarsan Balakrishnan The ground-state decay of 134Sb (t1/2 = 0.78 ± 0.06s) is reported to be dominated by a 0- → 0+ first-forbidden Gamow-Teller transition to the 134Te ground state (Iβ = 97.6%, Qβ = 8.515 MeV). A previous recoil-ion time-of-flight (RI-TOF) spectroscopy measurement of 134Sb with the Beta-decay Paul Trap (BPT) indicated that the ground-state feeding of 134Te is weaker than reported. The RI-TOF results were reproduced with a subsequent simulation of 134Sb ground-state decays to a theorised 5-MeV state fed with ∼17% of the total β-decay strength. To search for higher energy states and transitions, the X-Array and Scintillator and Tape Using Radioactive Nuclei (SATURN) decay station were used to study 134g,mSb decay using beams from the Californium Rare Isotope Breeder Upgrade (CARIBU) at Argonne National Laboratory (ANL). The experimental details, analysis, and updated nuclear data information will be presented. |
Friday, December 1, 2023 11:15AM - 11:30AM |
L10.00010: Octupole phonon excitations on the shell-model states in Xe, Cs, and Ba isotopes up to mass 142 Naotaka Yoshinaga, Koji Higashiyama, Chinatsu Watanabe Large-scale nuclear shell-model calculations are performed in Xe, Cs, and Ba isotopes up to mass 142 (Z ≥ 50 and N ≥ 82) beyond 132Sn. All the single-particle levels in the one-major shells, six neutron (1f7/2, 2p3/2, 2p1/2, 0h9/2, 1f5/2 and 0i13/2) orbitals and five proton (0g7/2, 1d5/2, 1d3/2, 0h11/2, and 0s1/2) orbitals are considered. For an effective two-body interaction, only one set of the multipole pairing, quadrupole-quadrupole interactions is employed and the strengths of the two-body interactions are set constant for all the nuclei considered. These interactions are phenomenologically determined to reproduce the experimental energy spectra in two-body systems. Some of the isomeric states are analyzed in terms of the shell-model configurations. Octupole correlated states are discussed by phenomenologically introducing a collective octupole phonon on top of each shell model state. |
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