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Journal Articles

First observation of $$^{28}$$O

Kondo, Yosuke*; Achouri, N. L.*; Al Falou, H.*; Atar, L.*; Aumann, T.*; Baba, Hidetada*; Boretzky, K.*; Caesar, C.*; Calvet, D.*; Chae, H.*; et al.

Nature, 620(7976), p.965 - 970, 2023/08

https://doi.org/10.1038/s41586-023-06352-6
 Times Cited Count：53 Percentile：95.82(Multidisciplinary Sciences)

no abstracts in English

Journal Articles

Intruder configurations in $$^{29}$$Ne at the transition into the island of inversion; Detailed structure study of $$^{28}$$Ne

Wang, H.*; Yasuda, Masahiro*; Kondo, Yosuke*; Nakamura, Takashi*; Tostevin, J. A.*; Ogata, Kazuyuki*; Otsuka, Takaharu*; Poves, A.*; Shimizu, Noritaka*; Yoshida, Kazuki; et al.

Physics Letters B, 843, p.138038_1 - 138038_9, 2023/08

https://doi.org/10.1016/j.physletb.2023.138038
 Times Cited Count：8 Percentile：74.52(Astronomy & Astrophysics)

Detailed $$gamma$$-ray spectroscopy of the exotic neon isotope $$^{28}$$Ne has been performed using the one-neutron removal reaction from $$^{29}$$Ne. Based on an analysis of parallel momentum distributions, a level scheme with spin-parity assignments has been constructed for $$^{28}$$Ne and the negative-parity states are identified for the first time. The measured partial cross sections and momentum distributions reveal a significant intruder p-wave strength providing evidence of the breakdown of the N = 20 and N = 28 shell gaps. Only a weak, possible f-wave strength was observed to bound final states. Large-scale shell-model calculations with different effective interactions do not reproduce the large p-wave and small f-wave strength observed experimentally, indicating an ongoing challenge for a complete theoretical description of the transition into the island of inversion along the Ne isotopic chain.

Journal Articles

Quasifree neutron knockout reaction reveals a small $$s$$-Orbital component in the Borromean nucleus $$^{17}$$B

Yang, Z. H.*; Kubota, Yuki*; Corsi, A.*; Yoshida, Kazuki; Sun, X.-X.*; Li, J. G.*; Kimura, Masaaki*; Michel, N.*; Ogata, Kazuyuki*; Yuan, C. X.*; et al.

Physical Review Letters, 126(8), p.082501_1 - 082501_8, 2021/02

AA2020-0819.pdf:1.29MB

https://doi.org/10.1103/PhysRevLett.126.082501
 Times Cited Count：92 Percentile：97.13(Physics, Multidisciplinary)

A quasifree ($$p$$,$$pn$$) experiment was performed to study the structure of the Borromean nucleus $$^{17}$$B, which had long been considered to have a neutron halo. By analyzing the momentum distributions and exclusive cross sections, we obtained the spectroscopic factors for $$1s_{1/2}$$ and $$0d_{5/2}$$ orbitals, and a surprisingly small percentage of 9(2)% was determined for $$1s_{1/2}$$. Our finding of such a small $$1s_{1/2}$$ component and the halo features reported in prior experiments can be explained by the deformed relativistic Hartree-Bogoliubov theory in continuum, revealing a definite but not dominant neutron halo in $$^{17}$$B. The present work gives the smallest $$s$$- or $$p$$-orbital component among known nuclei exhibiting halo features and implies that the dominant occupation of $$s$$ or $$p$$ orbitals is not a prerequisite for the occurrence of a neutron halo.

Journal Articles

Spallation and fragmentation cross sections for 168 MeV/nucleon $$^{136}$$Xe ions on proton, deuteron, and carbon targets

Sun, X. H.*; Wang, H.*; Otsu, Hideaki*; Sakurai, Hiroyoshi*; Ahn, D. S.*; Aikawa, Masayuki*; Fukuda, Naoki*; Isobe, Tadaaki*; Kawakami, Shunsuke*; Koyama, Shumpei*; et al.

Physical Review C, 101(6), p.064623_1 - 064623_12, 2020/06

https://doi.org/10.1103/PhysRevC.101.064623
 Times Cited Count：8 Percentile：54.27(Physics, Nuclear)

The spallation and fragmentation reactions of $$^{136}$$Xe induced by proton, deuteron and carbon at 168 MeV/nucleon were studied at RIKEN Radioactive Isotope Beam Factory via the inverse kinematics technique. The cross sections of the lighter products are larger in the carbon-induced reactions due to the higher total kinetic energy of carbon. The energy dependence was investigated by comparing the newly obtained data with previous results obtained at higher reaction energies. The experimental data were compared with the results of SPACS, EPAX, PHITS and DEURACS calculations. These data serve as benchmarks for the model calculations.

Journal Articles

Enhancement of element production by incomplete fusion reaction with weakly bound deuteron

Wang, H.*; Otsu, Hideaki*; Chiga, Nobuyuki*; Kawase, Shoichiro*; Takeuchi, Satoshi*; Sumikama, Toshiyuki*; Koyama, Shumpei*; Sakurai, Hiroyoshi*; Watanabe, Yukinobu*; Nakayama, Shinsuke; et al.

Communications Physics (Internet), 2(1), p.78_1 - 78_6, 2019/07

https://doi.org/10.1038/s42005-019-0165-1
 Times Cited Count：10 Percentile：53.52(Physics, Multidisciplinary)

Searching for effective pathways for the production of proton- and neutron-rich isotopes through an optimal combination of reaction mechanism and energy is one of the main driving forces behind experimental and theoretical nuclear reaction studies as well as for practical applications in nuclear transmutation of radioactive waste. We report on a study on incomplete fusion induced by deuteron, which contains one proton and one neutron with a weak binding energy and is easily broken up. This reaction study was achieved by measuring directly the cross sections for both proton and deuteron for $$^{107}$$Pd at 50 MeV/u via inverse kinematics technique. The results provide direct experimental evidence for the onset of a cross-section enhancement at high energy, indicating the potential of incomplete fusion induced by loosely-bound nuclei for creating proton-rich isotopes and nuclear transmutation of radioactive waste.

Oral presentation

The Determination of the initial $$^{146}$$Sm abundance of the outer Solar System

Masaki, Shumpei*; Haba, Makiko*; Yokoyama, Tetsuya*; Kagami, Saya

no journal, , 

Recently, an "isotopic dichotomy" has been identified between carbonaceous (CC) and non-carbonaceous (NC) meteorites. This dichotomy may reflect the differences in the location where the meteorite parent bodies were formed, indicating that CC and NC materials originated in the outer and inner regions of the Solar System, respectively. While many differentiated meteorites belong to the NC meteorites, some unclassified achondrites exhibit CC-like isotopic compositions. Northwest Africa (NWA) 6693/6704 are CC-like achondrites showing isotopic affinity with CR chondrites. The short-lived $$^{146}$$Sm has a half-life of 103 million years and decays into $$^{142}$$Nd by alpha emission. The initial $$^{146}$$Sm/$$^{144}$$Sm ratios are important for understanding the evolution of planetary materials in the early Solar System. These isotopic ratios in the NC meteorites and CAIs have been reported, but no data in the CC meteorites have not been obtained yet. In this study, we conducted high-precision Nd isotope analyses of NWA 6693 by TIMS. The results show that the initial $$^{146}$$Sm/$$^{144}$$Sm ratio in NWA 6693 are consistent with those in the NC meteorites and in CAIs.

Oral presentation

Toward the determination of the initial $$^{146}$$Sm abundance of outer Solar System

Masaki, Shumpei*; Haba K., Makiko*; Yokoyama, Tetsuya*; Kagami, Saya

no journal, , 

Recent studies on isotopic compositions of various elements have confirmed the isotopic dichotomy between carbonaceous (CC) and non carbonaceous (NC) meteorites, which presumably originated from the outer and inner Solar System, respectively. NWA 6693 is one of the carbonaceous achondrites, unlike most achondrites derived from differentiated parent bodies. $$^{146}$$Sm is an extinct nuclide having a half life of 103 million years. The accurate and precise initial $$^{146}$$Sm abundance of the Solar System is needed for utilizing the $$^{146}$$Sm-$$^{142}$$Nd chromometer to date the planetary material evolution in the early Solar System. The objective of this study is to obtain the initial $$^{146}$$Sm abundance from NWA 6693 and compare it with those obtained from CAI and NC meteorites. In this study, mineral separation was conducted for NWA 6693 to obtain the $$^{146}$$Sm-$$^{142}$$Nd mineral isochron. The specimens of NWA 6693 were crushed and sieved using nylon meshes having different mesh sizes. The sieved grains were further separated into mineral phases by using a neodymium magnet. These procedures made fractions having different magnetic properties, which are expected to correspond to orthopyroxene-olivine (magnetic fraction) and plagioclase (non magnetic fraction). To confirm the constituent minerals in each fraction, the representative grains were handpicked and made one sample from non magnetic fraction and three samples from magnetic fraction, followed by dissolving. The non magnetic fraction yielded the CI normalized REE pattern showing LREE enriched trend with positive Eu anomaly, suggesting that this fraction is dominantly composed of plagioclase. In contrast, the REE patterns of two magnetic fractions yielded flat to LREE enriched trends with negative Eu anomalies. These trends are different from the REE pattern of orthopyroxene. This result suggests that the magnetic fractions contain not only orthopyroxene and olivine but also other mineral, possibly phosphate.

7 (Records 1-7 displayed on this page)
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