中性子過剰核の特異な構造を通じた核子間対相互作用の解明

• Project/Area Number: 13J01876
• Research Category: Grant-in-Aid for JSPS Fellows
• Allocation Type: Single-year Grants
• Section: 国内
• Research Field: 素粒子・原子核・宇宙線・宇宙物理(実験)
• Research Institution: Osaka University
• Principal Investigator: 西畑 洸希 大阪大学, 理学研究科, 特別研究員(DC1)
• Project Period (FY): 2013-04-01 – 2016-03-31
• Project Status: Completed (Fiscal Year 2015)
• Budget Amount: ¥3,600,000 (Direct Cost: ¥3,600,000); Fiscal Year 2015: ¥1,200,000 (Direct Cost: ¥1,200,000); Fiscal Year 2014: ¥1,200,000 (Direct Cost: ¥1,200,000); Fiscal Year 2013: ¥1,200,000 (Direct Cost: ¥1,200,000)
• Keywords: 不安定原子核 / 中性子過剰核 / 放射線計測 / Mgアイソトープ

Outline of Annual Research Achievements

本研究の目的は、Mg同位体の系統的な準位構造の解明を行うことで、中性子過剰な原子核の構造を明らかにすることである。特に、本研究では中性子過剰な31Mgの準位構造を詳細に調べた。31Mgを含む中性子過剰な中性子数20近傍の質量領域は、安定核付近の原子核構造を非常によく説明してきた殻模型では説明できない状態が報告されており、注目を集めている。その構造を解き明かすために、様々な手法を用いて実験が行われてきた。しかし、31Mgについて詳細に明らかになっているのはほぼ基底状態に限られ、励起状態については基本的物理量であるスピン・パリティさえわかっていなかった。本研究では、昨年度カナダのTRIUMF研究所で、スピンを空間的にそろえた31Naのベータ崩壊によりそこから放出されるベータ線の非対称度を測定し、31Mgの励起状態のスピン・パリティを一度に決定する実験を行った。その解析の結果、31Mgの励起状態の5つの正パリティの状態のスピンを決定し、それに加え、過去に報告されていなかった11のガンマ遷移と2つの励起状態を新たに発見した。実験では31Mgに加えて、30Mgについてもデータを得ることができ、新たに３つの状態についてスピン・パリティを決定するなど大幅に準位構造を更新した。得られた準位構造について、その構造を調べるため理論計算と比較を行い、それぞれ30Mgと31Mgの励起状態における特徴的な構造が明らかとなった。30Mgでは、殻模型で説明できる状態と大きく変形した状態が比較的近い励起エネルギーで混在していることが分かった。31Mgでは、大きく変形した状態やそれが回転運動をしているという集団運動状態が低励起に存在するとともに、殻模型的な状態もやや高い励起エネルギーに存在していることが明らかとなった。

Research Progress Status

27年度が最終年度であるため、記入しない。

Strategy for Future Research Activity

27年度が最終年度であるため、記入しない。

Research Products

• [Journal Article] New isomer found in 140_51Sb89: sphericity and shell evolution between N=82 and N=90 (2016)
  • Author(s): R. Lozeva, H. Naidja, F. Nowacki, J. Dudek, A. Odahara, C.-B. Moon, S. Nishimura, P. Doornenbal, J.-M. Daugas, P.-A. Soderstrom, T. Sumikama, G. Lorusso, J. Wu, Z.Y. Xu, et al.
  • Journal Title: Physical Review C Volume: 93 Issue: 1 Pages: 014316-014316
  • DOI: 10.1103/physrevc.93.014316
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Decay spectroscopy of 160Sm: The lightest four-quasiparticle K isomer (2016)
  • Author(s): Z. Patel, Zs. Podolyak, P.M. Walker, P.H. Regan, P.-A. Soderstrom, H. Watanabe, E. Ideguchi, G.S. Simpson, S. Nishimura, F. Browne, P. Doornenbal, G. Lorusso, S. Rice, L. Sinclair, T. Sumikama, J. Wu, Z.Y. Xu, et al.
  • Journal Title: Physics Letters B Volume: 753 Pages: 182-186
  • DOI: 10.1016/j.physletb.2015.12.026
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] High-spin states in 136La and possible structure change in the N=79 region (2015)
  • Author(s): H.Nishibata, R.Leguillon, A.Odahara, R. Yokoyama et al.
  • Journal Title: Physical Review C Volume: 91 Issue: 5 Pages: 054305-054305
  • DOI: 10.1103/physrevc.91.054305
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Lifetime measurements of the first 2+ states in 104, 106Zr: Evolution of ground-state deformations (2015)
  • Author(s): F. Browne, A.M. Bruce, T. Sumikama, I. Nishizuka, S. Nishimura, P. Doornenbal, G. Lorusso, P.-A. Soderstrom, H. Watanabe, R. Daido, Z. Patel, S. Rice, L. Sinclair, J. Wu, Z.Y .Xu, A. Yagi, et al.
  • Journal Title: Physics Letters B Volume: 750 Pages: 448-452
  • DOI: 10.1016/j.physletb.2015.09.043
  • Peer Reviewed / Open Access / Int'l Joint Research / Acknowledgement Compliant
• [Journal Article] β-delayed γ-ray spectroscopy of non-yrast states in 138Te near the neutron drip line (2015)
  • Author(s): P. Lee, C.-B. Moon, C.S. Lee, A. Odahara, R. Lozeva, A. Yagi, S. Nishimura, P. Doornenbal, G. Lorusso, P.-A. Soderstrom, T. Sumikama, H. Watanabe, et al.
  • Journal Title: Physical Review C Volume: 92 Issue: 4 Pages: 044320-044320
  • DOI: 10.1103/physrevc.92.044320
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] β-Decay Half-Lives of 110 Neutron-Rich Nuclei across the N=82 Shell Gap: Implications for the Mechanism and Universality of the Astrophysical r Process (2015)
  • Author(s): G. Lorusso, S. Nishimura, Z.Y. Xu, A. Jungclaus, Y. Shimizu, G.S. Simpson, P.-A. Soderstrom, H. Watanabe, F. Browne, P. Doornenbal, G. Gey, H.S. Jung, B. Meyer, T. Sumikama, J. Taprogge, Zs. Vajta, J. Wu, et al.
  • Journal Title: Physical Review Letters Volume: 114 Issue: 19 Pages: 192501-192501
  • DOI: 10.1103/physrevlett.114.192501
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] New decay scheme of the 136_51Sb85 6- isomer (2015)
  • Author(s): R. Lozeva, A. Odahara, C.-B. Moon, S. Nishimura, P. Doornenbal, H. Naidja, F. Nowacki, P.-A. Soderstrom, T. Sumikama, G. Lorusso, J. Wu, Z.Y. Xu, et al.
  • Journal Title: Physical Review C Volume: 92 Issue: 2 Pages: 024304-024304
  • DOI: 10.1103/physrevc.92.024304
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Two-hole structure outside 78Ni: Existence of a μs isomer of 76Co and β decay into 76Ni (2015)
  • Author(s): P.-A. Soderstrom, S. Nishimura, Z.Y. Xu, K. Sieja, V. Werner, P. Doornenbal, G. Lorusso, F. Browne, G. Gey, H.S. Jung, T. Sumikama, J. Taprogge, Zs. Vajta, H. Watanabe, J. Wu, et al.
  • Journal Title: Physical Review C Volume: 92 Issue: 5 Pages: 051305-051305
  • DOI: 10.1103/physrevc.92.051305
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Pathway for the production of neutron-rich isotopes around the N=126 shell closure (2015)
  • Author(s): Watanabe, Y.X.,Kim, Y.H., Jeong, S.C., Hirayama, Y., Imai, N., Ishiyama, H., Jung, H.S., Miyatake, H., Choi, S., Song, J.S., Clement, E., De France, G., Navin, A., Rejmund, M., Schmitt, C., Pollarolo, G., Corradi, L., Fioretto, E., Montanari, D., Niikura, Mi, Suzuki, D., Nishibata, H., Takatsu, J.
  • Journal Title: Physical Review Letters Volume: 115 Issue: 17 Pages: 172503-172503
  • DOI: 10.1103/physrevlett.115.172503
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] β-Decay Half-Lives of 76, 77Co, 79, 80Ni and 81Cu Experimental Indication of a Doubly Magic 78Ni (2014)
  • Author(s): Z.Y. Xu, S. Nishimura, G. Lorusso, F. Browne, P. Doornenbal, G. Gey, H.-S. Jung, Z. Li, M. Niikura, P.-A. Soderstrom, T. Sumikama, J. Taprogge, Zs. Vajta, H. Watanabe, J. Wu, A. Yagi, K. Yoshinaga, H. Baba, S. Franchoo, H. Nishibata 他
  • Journal Title: Phys. Rev. Lett. Volume: 113 Issue: 3 Pages: 032505-032505
  • DOI: 10.1103/physrevlett.113.032505
  • Peer Reviewed / Open Access
• [Journal Article] Monopole-Driven Shell Evolution below the Doubly Magic Nucleus 132Sn Explored with the Long-Lived Isomer in 126Pd (2014)
  • Author(s): H. Watanabe, G. Lorusso, S. Nishimura, T. Otsuka, K. Ogawa, Z.Y. Xu, T. Sumikama, P.-A. Soderstrom, P. Doornenbal, Z. Li, F. Browne, G. Gey, H.S. Jung, J. Taprogge, Zs. Vajta, J. Wu, A. Yagi, H. Baba, G. Benzoni, H. Nishibata 他
  • Journal Title: Phys. Rev. Lett. Volume: 113 Issue: 4 Pages: 042502-042502
  • DOI: 10.1103/physrevlett.113.042502
  • Peer Reviewed / Open Access
• [Journal Article] Yrast 6+ Seniority Isomers of 136, 138Sn (2014)
  • Author(s): G.S. Simpson, G. Gey, A. Jungclaus, J. Taprogge, S. Nishimura, K. Sieja, P. Doornenbal, G. Lorusso, P.-A. Soderstrom, T. Sumikama, Z.Y. Xu, H. Baba, F. Browne, N. Fukuda, N. Inabe, T. Isobe, H.S. Jung, D. Kameda, G.D. Kim, H. Nishibata 他
  • Journal Title: Phys. Rev. Lett. Volume: 113 Issue: 13 Pages: 132502-132502
  • DOI: 10.1103/physrevlett.113.132502
  • Peer Reviewed / Open Access
• [Journal Article] 1p3/2 Proton-Hole State in 132Sn and the Shell Structure Along N= 82 (2014)
  • Author(s): J. Taprogge, A. Jungclaus, H. Grawe, S. Nishimura, P. Doornenbal, G. Lorusso, G.S. Simpson, P.-A. Soderstrom, T. Sumikama, Z.Y. Xu, H. Baba, F. Browne, N. Fukuda, R. Gernhauser, G. Gey, N. Inabe, T. Isobe, H.S. Jung, D. Kameda, H. Nishibata 他
  • Journal Title: Phys. Rev. Lett. Volume: 112 Issue: 13 Pages: 132501-132501
  • DOI: 10.1103/physrevlett.112.132501
  • Peer Reviewed / Open Access
• [Journal Article] Identification of a millisecond isomeric state in 129Cd81 via the detection of internal conversion and Compton electrons (2014)
  • Author(s): J. Taprogge, A. Jungclaus, H. Grawe, S. Nishimura, Z.Y. Xu, P. Doornenbal, G. Lorusso, E. Nacher, G.S. Simpson, P.-A. Soderstrom, T. Sumikama, H. Baba, F. Browne, N. Fukuda, R. Gernhauser, G. Gey, N. Inabe, T. Isobe, H.S. Jung, H. Nishibata 他
  • Journal Title: Phys. Lett. B Volume: 738 Pages: 223-227
  • DOI: 10.1016/j.physletb.2014.09.047
  • Peer Reviewed / Open Access
• [Journal Article] Isomer Decay Spectroscopy of 164Sm and 166Gd: Midshell Collectivity Around N=100 (2014)
  • Author(s): Z. Patel, P.-A. Soderstrom, Zs. Podolyak, P.H. Regan, P.M. Walker, H. Watanabe, E. Ideguchi, G.S. Simpson, H.L. Liu, S. Nishimura, Q. Wu, F.R. Xu, F. Browne, P. Doornenbal, G. Lorusso, S. Rice, L. Sinclair, T. Sumikama, J. Wu, H. Nishibata 他
  • Journal Title: Phys. Rev. Lett. Volume: 113 Issue: 26 Pages: 262502-262502
  • DOI: 10.1103/physrevlett.113.262502
  • Peer Reviewed
• [Journal Article] Nuclear structure explored by β-delayed decay spectroscopy of spin-polarized radioactive nuclei at TRIUMF ISAC-1 (2014)
  • Author(s): T. Shimoda, K. Tajiri, K. Kura, A. Odahara, M. Suga, Y. Hirayama, N. Imai, H. Miyatake, M. Pearson, C. D. P. Levy, K. P. Jackson, R. Legillon, C. Petrache, T. Fukuchi, N. Hamatani, T. Hori, M. Kazato, Y. Kenmoku, T. Masue, H. Nishibata, T. Suzuki, A. Takashima, R. Yokoyama
  • Journal Title: Hyperfine Interactions Volume: 225 Issue: 1-3 Pages: 183-191
  • DOI: 10.1007/s10751-013-0895-5
  • Peer Reviewed
• [Journal Article] Shape evolution in ^<116,118>Ru : Triaxiality and transition between the O (6) and U (5) dynamical symmetries (2013)
  • Author(s): P. -A. Soderstrom, G. Lorusso, H. Watanabe, S. Nishimura, P. Doornenbal, G. Thiamova, F. Browne, G. Gey, H. S. Jung, T. Sumikama, J. Taprogge, Zs. Vajta, J. Wu, Z. Y . Xu, H. Baba, G. Benzoni, K. Y. Chae, F. C. L. Crespi, N. Fukuda, H. Nishibata, 他
  • Journal Title: Physical Review C Volume: 88
  • Peer Reviewed
• [Journal Article] Isomers in ^<128>Pd and ^<128>Pd : Evidence for a robust shell closure at the neutron magic number 82 in exotic Palladium isotopes (2013)
  • Author(s): H. Watanabe, G. Lorusso, S. Nishimura, Z. Y. Xu, T. Sumikama, P. -A. Soderstrom, P. Doornenbal, F. Browne, G. Gey, H. S. Jung, J. Taprogge, Zs. Vajta, J. Wu, A. Yagi, H. Baba, G. Benzoni, K. Y. Chae, F. C. L. Crespi, N. Fukuda, H. Nishibata, 他
  • Journal Title: Physical Review Letters Volume: 111
  • Peer Reviewed
• [Journal Article] Spectroscopy of ^<135>La (2013)
  • Author(s): R. Leguillon, H. Nishibata, Y. Ito, C. M. Petrache, A. Odahara, T. Shimoda, N. Hamatani, K. Tajiri, J. Takatsu, R. Yokoyama, E. Ideguchi, H. Watanabe, Y. Wakabayashi, K. Yoshinaga, T. Suzuki, S. Nishimura, D. Beaumel, G. Lehaut, D. Guinet, P. Desesquelles, D. Curien, A. Astier, T. Konstantinopoulos, T. Zerrouki
  • Journal Title: Physical Review C Volume: 88
  • Peer Reviewed
• [Journal Article] Study of collisions of ^<136>Xe + ^<198>Pt for the KEK isotope separator (2013)
  • Author(s): Y. X. Watanabe, Y. Hirayama, N. Imai, H. Ishiyama, S. C. Jeong, H. Miyatake, E. Clement, G. de France, A. Navin, M. Rejmund, C. Schmitt, G. Pollarolo, L. Corradi, E. Fioretto, D. Montanari, S. H. Choi, Y. H. Kim, J. S. Song, M. Niikura, D. Suzuki, H. Nishibata, J. Takatsu
  • Journal Title: Nuclear Instruments and Methods in Physics Res earch Section B Volume: 317 Pages: 752-755
  • Peer Reviewed
• [Journal Article] Production cross section measurements of radioactive isotopes by BigRIPS separator at RIKEN RI Beam Factory (2013)
  • Author(s): H. Suzuki, T. Kubo, N. Fukuda, N. Inabe, D. Kameda, H. Takeda, K. Yoshida, K. Kusaka, Y. Yanagisawa, M. Ohtake, H. Sato, Y. Shimizu, H. Baba, M. Kurokawa, T. Ohnishi, K. Tanaka, O. B. Tarasov, D. Bazin, D. J. Morrissey, H. Nishibata, 他
  • Journal Title: Nuclear Instruments and Methods in Physics Research Section B Volume: 317 Pages: 756-758
  • Peer Reviewed
• [Presentation] Study of exotic structures in neutron-rich 30Mg and 31Mg by spin-polarized radioactive beam (2015)
  • Author(s): H. Nishibata, T. Shimoda, A. Odahara, S. Morimoto, S. Yoshida, A. Yagi, H. Kanaoka, T. Kawamura, A. Nakahashi, T. Fujiwara, T. Yoshizumi, M. Pearson, C. D. P. Levy
  • Organizer: Gamma15
  • Place of Presentation: 大阪大学・大阪府豊中市
  • Year and Date: 2015-10-01
  • Int'l Joint Research
• [Presentation] 偏極不安定核Naビームを用いた中性子過剰Mg同位体の構造研究 (2015)
  • Author(s): 西畑 洸希, 下田 正, 小田原 厚子, 森本 翔太, 吉田 晋之介, 八木 彩祐未, 金岡 裕志, 河村 嵩之, 中橋 晶, 藤原 智貴,吉住 孝之, M. Pearson, C.D.P. Levy
  • Organizer: 日本物理学会
  • Place of Presentation: 大阪市立大学・大阪府大阪市
  • Year and Date: 2015-09-25
• [Presentation] 偏極不安定核31Naビームを用いた中性子過剰な31Mgの構造の研究 (2015)
  • Author(s): 西畑洸希, 下田正, 小田原厚子, 森本翔太, 吉田晋之介, 八木彩祐未, 金岡裕志, 河村嵩之, 中橋晶, 藤原智貴, 吉住孝之, M. Pearson, C. D. P. Levy
  • Organizer: 日本物理学会秋季大会
  • Place of Presentation: 早稲田大学, 東京都・新宿区
  • Year and Date: 2015-03-21 – 2015-03-24
• [Presentation] Study of structure change in neutron-rich Mg isotopes by spin-polarized radioactive beam (2014)
  • Author(s): H. Nishibata, T. Shimoda, A. Odahara, and S1391 Collaboration
  • Organizer: 4th Joint Meeting of the Nuclear Physics Divisions of the American Physical Society and the Physical Society of Japan
  • Place of Presentation: Hawaii, America
  • Year and Date: 2014-10-07 – 2014-10-11