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 E10: Nuclear Structure III |
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Chair: Daiki Nishimura Room: Hilton Waikoloa Village Kohala 3 |
Wednesday, November 29, 2023 7:00PM - 7:15PM |
E10.00001: Half-life measurement of the107-keV isomeric state in 45Cr Mei Amitani, Yuki Nakamura, Chihaya Fukushima, Daiki Nishimura, Shin'ichiro Michimasa, Shutaro Hanai, Eiji Ideguchi, Nobuaki Imai, Keita Kawata, Hiroki Nishibata, Kodai Okawa, Takeshi Y Saito, Daisuke Suzuki, Hiroyuki Takahashi, Hisato Tanaka, Rin Yokoyama The atomic nuclei near the self-conjugate line at Z=21 or N=21 are known to systematically have spin-gap isomers formed by low-lying d3/2 and f7/2 orbitals. In 42-47Sc isotopes, isomers with the d3/2-hole configuration have already been reported, while some of the mirror configuration isomers within the N=21 isotones remain unreported. |
Wednesday, November 29, 2023 7:15PM - 7:30PM |
E10.00002: First beta-delayed neutron spectroscopy of neutron-rich Cl isotopes with FDSi Ian C Cox, Zhengyu Xu, Noritaka Kitamura, Robert Grzywacz, Wei Jia Ong, James M Allmond, Aleksandra Fijalkowska, Marek Karny, Bertis C Rasco, Krzysztof Piotr P Rykaczewski, Hendrik Schatz, Bradley M Sherrill, Kevin Siegl, Oleg B Tarasov, Rin Yokoyama The first experimental campaigns with FRIB Decay Station Initiator [1] at FRIB focused on the spectroscopy of very neutron-rich isotopes near the N=28 island of inversion. They provided a wealth of data on beta-delayed neutron emitters. We will present the first complete beta decay spectroscopy along the N=28 shell closure as it evolves from a spherical 48Ca toward a strongly deformed 42Si, using a combination of high-resolution neutron (NEXTi) and gamma-ray (DEGAi) data alongside total absorption spectroscopy data (MTAS). The beta-decay strength distribution of 45Cl was extracted up to 8 MeV, including the feedings to both neutron bound and unbound states in 45Ar, and is compared with the large-scale shell model calculations by Yohsida, et al. [2]. This experiment provides the first test of these predictions for the dominant Gamow-Teller transitions in this region. The importance of the discrepancies between model predictions and experimental data will be discussed, including a spin reassignment for the ground state in 45Cl. |
Wednesday, November 29, 2023 7:30PM - 7:45PM |
E10.00003: Investigating Nuclear Shell Evolution in Neutron-Rich Calcium Isotopes Robin Coleman, Carl E Svensson, Corrina Andreoiu, Gordon C Ball, Soumendu S Bhattacharjee, Harris Bidaman, Vinzenz Bildstein, Samantha Buck, Grace Carpenter, Fatima H. Garcia, Adam B Garnsworthy, Paul E Garrett, Christopher Griffin, Gwen F Grinyer, Madeleine Hanley, Alex T Laffoley, Rebeka S Lubna, Andrew D MacLean, Matthew S Martin, Connor R Natzke, Bruno Olaizola, Charlotte E Paxman, Carlotta Porzio, Allison J Radich, Marco Rocchini, Frederic Sarazin, Stephen Shadrick, S Sharma, Alireza Talebitaher, Victoria Vedia, Kenneth A Whitmore, Frank Wu, Daniel Yates, Tammy Zidar Nuclei away from the line of stability have been found to demonstrate behavior that is inconsistent with the traditional magic numbers of the spherical shell model. This has led to the concept of the evolution of nuclear shell structure in exotic nuclei, and the neutron-rich calcium isotopes are a key testing ground of these theories; there have been conflicting results from various experiments as to the true nature of a sub-shell closure for neutron-rich nuclei around 52Ca. An experiment was performed at the ISAC facility of TRIUMF; 52K, 53K, and 54K were delivered to the GRIFFIN gamma-ray spectrometer paired with the SCEPTAR and the ZDS ancillary detectors for beta-tagging, as well as DESCANT for neutron-tagging. Using this powerful combination of detectors, we combine the results to construct level schemes for the isotopes populated in the subsequent beta-decay. Preliminary results from the analysis of the gamma, beta, and neutron spectra will be presented and discussed in the context of shell model calculations in neutron-rich nuclei. |
Wednesday, November 29, 2023 7:45PM - 8:00PM |
E10.00004: Collinear Laser Spectroscopy on Neutron-Deficient Al Isotopes Brooke J Rickey, Ivana Belosevic, Alex Brinson, Jonas Karthein, Kristian Koenig, Jeremy Lantis, Bernhard Maass, Kei Minamisono, Wilfred Noertershaeuser, Skyy V Pineda, Dominic M Rossi, Ronald Fernando Garcia Ruiz, Silviu-Marian Udrescu, Adam R Vernon, Shane G Wilkins A large reaction cross section [1] in 23Al and a large isospin asymmetry in the mass A=22 system [2] of 22Al suggest their proton halo structures. However, the last proton presumably occupies the d5/2 orbital in the ground state, making the proton halo structures’ existence not decisive. In an upcoming experiment at the BECOLA facility at FRIB, charge radii and electromagnetic moments will be determined through isotope shift measurements to directly address the proton distributions in 22, 23Al. The newly commissioned Resonance Ionization Spectroscopy Experiment (RISE) setup will be used for laser spectroscopy. The experimental detail will be discussed, as well as the commissioning of RISE. |
Wednesday, November 29, 2023 8:00PM - 8:15PM |
E10.00005: Collectivity of 30,31Na studied via Heavy-Ion Inelastic Scattering Roy Salinas, Hironori Iwasaki, Aldric Revel, Jin Wu, Jun Chen, John Ash, Daniel Bazin, Peter Farris, Alexandra Gade, Mara Grinder, Nobu Kobayashi, Jing Li, Brenden R Longfellow, Tea Mijatović, Jorge Pereira, Andrew Sanchez, Mark Spieker, Dirk W Weisshaar, Robert Elder Near the beta stability line, nuclei with magic numbers are expected to exhibit spherical ground states, accompanied by reduced B(E2) values for low-lying state excitations. However, as we approach the neutron-rich region, the so-called island of inversion, along the N=20 magic number, unexpected behavior has been suggested by the enhancement in measured B(E2) values and ground-state quadrupole moments. Such measurements enable us to test theoretical models utilizing particle-hole excitations between the sd and fp shells to describe collective behavior within this region, allowing a comparison to be made with experiment. A heavy-ion inelastic scattering measurement on neutron-rich 30,31Na isotopes at N=19,20 was conducted at the NSCL with a modified recoil distance setup utilizing the TRIPLEX plunger, GRETINA, and the S800 spectrograph. We measured the E2 transition rates within members of suggested rotational bands for the K=2, 2+ ground-state in 30Na and the K=3/2, 3/2(+) ground-state in 31Na. This allows us to further discern the role of collective modes in the low-lying transitions and the extent of ground-state deformation near N=20. A preliminary result of the experimental cross sections for 30,31Na will be presented alongside a discussion on extracted B(E2) values with available theoretical calculations. |
Wednesday, November 29, 2023 8:15PM - 8:30PM |
E10.00006: Muon nuclear capture reaction on 28,29,30Si Rurie Mizuno, Megumi Niikura, Takeshi Y Saito, Teiichiro Matsuzaki, Yuji Yamaguchi, Shinichiro Abe, Hiroya Fukuda, Masanori Hashimoto, Adrian Hillier, Katsuhiko Ishida, Naritoshi Kawamura, Shoichiro Kawase, Teppei Kawata, Kentaro Kitafuji, Hiroyuki Matsuzaki, Futoshi Minato, Masaya Oishi, Partick Strasser, Akira Sato, Koichiro Shimomura, Soshi Takeshita, Dai Tomono, Izumi Umegaki The muon nuclear capture is a reaction of a negative muon and a proton in nuclei via weak interaction. The reaction produces an excited nucleus, from which several particles are emitted. The experimental data concerning the muon nuclear capture, especially about the distributions of the excited states, such as the branching ratio (BR) of residual nuclei and the energy distributions of emitted particles, are limited for the moment. And there is also no established model that can describe the muon nuclear capture and its following particle emissions. The production BR of each daughter nucleus resulting from the muon capture of silicon was measured with some methods, but these methods contain several assumptions and show some discrepancies in the number of charged particle emissions. Therefore, we measured the absolute production BR of the muon capture to obtain accurate data and evaluate the excitation states of Si isotopes after the muon capture. |
Wednesday, November 29, 2023 8:30PM - 8:45PM |
E10.00007: Effects of two-particle two-hole configurations on particle emissions following muon capture Futoshi Minato, Tomoya Naito, Osamu Iwamoto Nuclei are excited by muon capture reactions. If the excitation energy is above particle thresholds, the nuclei emit particles competing with the gamma-ray deexcitation. The typical examples are neutron and proton emissions. Other charged particles emissions, like deuteron-, 3He-, triton-, α-emissions, also occur if the nuclear excitation energy is very high. Information on these particle emissions is important for evaluating soft errors of semi-conductors and radioactivities of materials after irradiations of muon beams. Although experimental data of the particle emissions following muon captures have been reproduced with some phenomenological models, the detailed mechanism with respect to the nuclear structure is still unclear. In particular, experimentally measured neutron spectra after muon capture cannot be reproduced well. We worked on solving this issue with a microscopic approach of second-order proton-neutron Tamm-Dancoff-approximation and particle evaporation models considering pre-equilibrium and compound process. We found that the two-particle two-hole configurations play an important role to reproduce particle spectra obtained after muon captures. |
Wednesday, November 29, 2023 8:45PM - 9:00PM |
E10.00008: The l-forbidden M1 transitions in chlorine isotopes around N = 28 shell closure Yasutaka Yamamoto, Nori Aoi, Michael P Carpenter, Pieter Doornenbal, Yongde Fang, Thi Ha Hoang, Eiji Ideguchi, Satoko Iwazaki, Asahi Kohda, Takuma Koiwai, Mukhi Kumar Raju, Benoit Mauss, Hooi Jin ONG, Thanh Tung Pham, Daisuke Suzuki, Dinh Trong Tran, Kathrin Wimmer The effect of meson exchange current in nuclei is studied via l-forbidden (△l=2, △J=1) M1 transitions. The M1 transitions are caused by the single-particle-like transition of valence nucleons, the core excitation, and the meson exchange current. In the l-allowed (△l=0, △J=1) M1 transition, the single-particle-like transition and the core excitation are the dominant effects and the meson exchange current is very small. On the other hand, in the l-forbidden M1 transition, the meson exchange current measurably affects the transition strengths. Therefore, information about the meson exchange current is extracted from the l-forbidden M1 transition strengths. To measure the l-forbidden M1 transition strengths, we carried out the in-beam gamma-ray spectroscopy experiments of chlorine isotopes at RCNP (CAGRA campaign) and RIBF (HiCARI campaign). The l-forbidden M1 transition strengths were obtained from the transition lifetimes measured by the Doppler shift attenuation method with Ge detectors. In this presentation, we will report the analysis results of experiments and the contribution of the meson exchange current in the l-forbidden M1 transition strengths. |
Wednesday, November 29, 2023 9:00PM - 9:15PM |
E10.00009: Investigating Shell Structure: Mass Measurements of Sc, Ti, and V Isotopes at new magic N = 32 and N = 34 Shun Iimura, Marco Rosenbusch, Aiko Takamine, Yusuke Tsunoda, Michiharu Wada, Sidong Chen, Dongsheng Hou, Wenduo Xian, Hironobu Ishiyama, Shuxiong Yan, Peter Schury, Heather L Crawford, Pieter Doornenbal, Yoshikazu Hirayama, Yuta Ito, Sota Kimura, Takuma Koiwai, Takao M Kojima, Hiroyuki Koura, Jenny H. C. Lee, Jiajian Liu, Shin'ichiro Michimasa, Hiroari Miyatake, Jun-young Moon, Shunji Nishimura, Sarah Naimi, Toshitaka Niwase, Atsuko Odahara, Takaharu Otsuka, Stefanos Paschalis, Marina Petri, Noritaka Shimizu, Tetsu Sonoda, Daisuke Suzuki, Yutaka X Watanabe, Kathrin Wimmer, Hermann Wollnik In this study, we present our findings on the precise mass measurements of 55Sc, 55-58Ti, and 55-59V isotopes. These measurements were obtained during the initial commissioning campaign of the ZD-MRTOF system at the RIBF/RIKEN. Our focus is to examine the implications of these masses on the shell structure at N=32 and N=34, specifically in relation to the deformation towards N=40. The experimental setup, newly installed downstream of the ZeroDegree (ZD) spectrometer at the BigRIPS facility (RIBF/RIKEN), consists of a radiofrequency (RF) carpet-type helium gas cell combined with a multi-reflection time-of-flight (MRTOF) mass spectrograph. In the first low-energy experiment conducted at BigRIPS, high-energy products were decelerated and captured in helium gas. Subsequently, they were extracted through an aperture via RF microstructure into a Paul trap ion guide structure. The cooled and thermalized ions were then injected into the MRTOF system, forming a high-quality beam for conducting high-precision mass measurements. We provide a detailed account of the new cryogenic gas cell and the mass analysis methods employed in this experiment. Additionally, we outline our future plans for mass measurements, particularly focusing on the N=126 region. This region is of significant interest as it is proximate to waiting point nuclei relevant to the third peak of the r-process. |
Wednesday, November 29, 2023 9:15PM - 9:30PM |
E10.00010: Search for α-cluster state in N = Z medium heavy nuclei Hidetoshi Akimune, J Gibelin, M N Harakeh, S Bagchi, Nasser Kalantar-Nayestanaki, Mamoru Fujiwara, Umesh Garg Inelastic α-scattering experiments on unstable N=Z double-magic 56Ni nuclei were performed at GANIL in inverse kinetics at an incident energy of 50 A.MeV. A high multiplicity of α-particle emission was observed within the limited phase space of the experimental setup. Such high multiplicity cannot be explained by statistical decay models. On the other hand, the simplified ideal classical gas model reproduces the experimental momentum distribution well with kT=0.4 MeV. However, since the energies of all decay particles were not measured in this experiment, nor were the kinetic energies of the recoiled α-particles, the excitation energies cannot be determined. Therefore, we assume that the α-gas state of 56Ni exists around 113 MeV and that the measured multiplicity is an ensemble of α-decays from various excitation energies, which reproduces the experimental results well. These results suggest that an exotic state consisting of a large number of α-particles may exist at the excitation energy of 113+15-17MeV. We propose a method to measure the energy and angular distribution of recoiled α-particles, which are estimated to have kinetic energies of a few MeV, in order to resolve the uncertainty of the excitation energy in this experiment. |
Wednesday, November 29, 2023 9:30PM - 9:45PM |
E10.00011: Simulation study to search for the α-condensed state in 24Mg by measuring 12C+12C scattering with AT-TPC Soki Sakajo, Takahiro Kawabata, Tatsuya Furuno, Yassid Ayyad It is well known that many light nuclei possess prominent cluster structures and the αparticle plays an important role as a constituent of the cluster state. As elucidated by the Ikeda diagram, the α-cluster structures are expected to emerge near the α-decay threshold energies. The α-condensed state, which is one of the α-cluster states, is of great interest because all the α clusters are condensed into the lowest-energy orbit and its density becomes dilute. The theoretical calculation by T. Yamada et al. suggested that the energy of the α-condensed state increases with the mass number, but they still exist up to A=40. However, the α-condensed states in A≥16 have never been experimentally established. Therefore, we proposed to search for the α-condensed state in 24Mg by measuring the 12C + 12C scattering with AT- TPC developed in Michigan State University. A 12C beam at 55 MeV will be injected to AT-TPC filled with isoC4H10 gas at about 0.1 atm, and the excitation-energy region of Ex =28.5̶40 MeV in 24Mg with the thick-target method. Because AT-TPC can track low-energy charged particles over large solid angles, it is useful for detecting multi-α particles emitted from the α-condensed state. For this experiment, we have conducted a simulation to examine the feasibility of the proposed experiment. In the present talk, we will report the intermediate results of the simulation. |
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