| Project/Area Number |
04452029
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
核・宇宙線・素粒子
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| Research Institution | RIKKYO UNIVERSITY |
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Principal Investigator |
MOTOBAYASHI Tohru RIKKYO UNIVERSITY COLLEGE OF SCIENCE ASSISTANT PROFESSOR, 理学部, 助教授 (20116114)
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| Co-Investigator(Kenkyū-buntansha) |
SHIMOURA Susumu RIKKYO UNIVERSITY COLLEGE OF SCIENCE LECTURER, 理学部, 講師 (10170995)
GEN Kenji RIKKYO UNIVERSITY COLLEGE OF SCIENCE PROFESSOR, 理学部, 教授 (40062583)
IEKI Kazuo RIKKYO UNIVERSITY COLLEGE OF SCIENCE ASSISTANT PROFESSOR, 理学部, 助教授 (10159577)
SHIRATO Shoji RIKKYO UNIVERSITY COLLEGE OF SCIENCE PROFESSOR, 理学部, 教授 (90062562)
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| Project Period (FY) |
1992 – 1993
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| Project Status |
Completed (Fiscal Year 1993)
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| Budget Amount *help |
¥7,000,000 (Direct Cost: ¥7,000,000)
Fiscal Year 1993: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 1992: ¥6,300,000 (Direct Cost: ¥6,300,000)
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| Keywords | NEUTRON-RICH NUCLEI / UNSTABLE NUCLEAR BEAM / COULOMB EXCITATION / E2 TRANSITION PROBABILITY / MAGNESIUM 32 |
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| Research Abstract |
The Coulomb excitation of a very neutron-rich nucleus ^<32>Mg to its 2^+ state was studied using an unstable nuclear beam of ^<32>Mg at 49 MeV/u with a ^<208>Pb target. The beam was generated by projectile fragmentation reaction induced by 94 MeV/u ^<40>Ar ions bombarding a ^9Be target, and separated by the RIPS facility, a system with essentially two dipole magnets with an energy loss degradeer, of RIKEN (the Institute of Physical and Chemical Research). A stuck of 64 NaI(Tl) scintillators were settled around the target to detect gamma-rays from the 2^+ state of ^<32>Mg in coincidence with inelastically scattered ^<32>Mg nuclei detected by silicon counter telescope consisting of five/400 mum thick silicon detectors. The silicon telescope provided particle identification to select the inelastic scattering. The relevant inelastic scattering cross section was obtained by integrating the gamma-ray yield with corrections due to the Doppler shift of the photon energy and the detection efficiencies of the gamma-ray detector and the silicon counter telescope.
The B(E2) value of 426(〕SY.+-.〔)34 e^2fm^2 was extracted by a coupled channel analysis. The value is in good agreement with a recent shell model prediction and also with a global phenomenological expression of the N_pN_n scheme. The major ingredient of these models is an obliteration of the N=20 shell closure. Therefore the presenct result confirms a large deformation of ^<32>Mg suggested by the low excitation energy of the 2^+ state, and points to the vanishing of the N=20 shell gap. The success of the present study opens up a new profound field of research to investigate a large number of unknown 0^+-2^+ transitions in unstable nuclei.
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