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Strong one-neutron emission from two-neutron unbound states in β decays of the r -process nuclei Ga 86,87

Yokoyama R. Department of Physics and Astronomy, University of Tennessee, Knoxville, TN 37996, United States|
Xu X.X. | Woods P.J. | Wolińska-Cichocka M. | Tolosa-Delgado A. | Thomas S.L. | Tarifeño-Saldivia A. | Takeda H. | Suzuki H. | Surman R. | Sumikama T. | Stracener D.W. | Singh M. | Simpson J. | Shimizu Y. | Sakurai H. | Saito Y. | Rubio B. | Rajabali M.M. | Pucknell V.F.E. | Prydderch M. | Piersa M. | Phong V.H. | Page R.D. | Nepal N. | Morrall P. | Morales A.I. | Montes F. | Miernik K. | Matsui K. | Madurga M. | Lorusso G. | Liu J. | Liang J. | Lazarus I. | Labiche M. | Kubono S. | Korgul A. | Kiss G.G. | King T.T. | Khiem L.H. | Kawano T. | Karny M. | Kahl D. | Isobe T. | Heideman J. | Harkness-Brennan L.J. | Hall O. | Ha J. Heavy Ion Laboratory, University of Warsaw, Pasteura 5A, Warsaw, PL-02-093, Poland| Griffin C.J. Department of Physics, University of Notre Dame, Notre Dame, IN 46656, United States| Go S. Department of Physics, Tennessee Technological University, Cookeville, TN 38505, United States| Fukuda N. STFC Rutherford Appleton Laboratory, Harwell Campus, Didcot, OX11 0QX, United Kingdom| Estrade A. Faculty of Physics, VNU University of Science, 334 Nguyen Trai, Thanh Xuan, Hanoi, Viet Nam| Domingo-Pardo C. National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI 48824, United States| Davinson T. Department of Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan| Cortes G. Department of Physics, University of Surrey, Guildford, GU2 7XH, United Kingdom| Coleman-Smith P.J. National Physical Laboratory (NPL), Teddington, Middlesex, TW11 0LW, United Kingdom| Calvino F. Department of Physics, University of Hong Kong, Pokfulam Road, Hong Kong| Caballero-Folch R. Department of Physics and Astronomy, McMaster University, Hamilton, ON L8S 4M1, Canada| Bruno C.G. Institute of Physics, Vietnam Academy of Science and Technology, 10 Dao Tan, Ba Dinh, Ha Noi, Viet Nam| Bae S. Los Alamos National Laboratory, Los Alamos, NM 87545, United States| Baba H. Faculty of Physics, University of Warsaw, Warsaw, PL-02-093, Poland| Agramunt J. Department of Physics, University of Liverpool, Liverpool, L69 7ZE, United Kingdom| Allmond J.M. Department of Physics and Science, Advanced Materials Program, Central Michigan University, Mount Pleasant, MI 48859, United States| Algora A. STFC Daresbury Laboratory, Daresbury, Warrington, WA4 4AD, United Kingdom| Nishimura S. School of Physics and Astronomy, University of Edinburgh, Edinburgh, EH9 3FD, United Kingdom| Tain J.L. Department of Physics and Astronomy, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul, 08826, South Korea| Dillmann I. MTA Atomki, Bem ter 18/c, Debrecen, H4032, Hungary| Rykaczewski K.P. RIKEN, Nishina Center, 2-1 Hirosawa, Wako, Saitama, 351-0198, Japan| Brewer N. Instituto de Fisica Corpuscular (CSIC-Universitat de Valencia), Valencia, E-46071, Spain| Rasco B.C. TRIUMF, Vancouver, BC V6T 2A3, Canada| Grzywacz R. Physics Division, Oak Ridge National Laboratory, Oak Ridge, TN 37830, United States|

Physical Review C Số 3, năm 2019 (Tập 100, trang -)

ISSN: 24699985

ISSN: 24699985

DOI: 10.1103/PhysRevC.100.031302

Tài liệu thuộc danh mục: Scopus

Article

English

Tóm tắt tiếng anh
β-delayed one-neutron and two-neutron branching ratios (P1n and P2n) have been measured in the decay of A=84 to 87 Ga isotopes at the Radioactive-Isotope Beam Factory (RIBF) at the RIKEN Nishina Center using a high-efficiency array of He3 neutron counters (BRIKEN). Two-neutron emission was observed in the decay of Ga84,85,87 for the first time and the branching ratios were measured to be P2n=1.6(2)%,1.3(2)%, and 10.2(28)stat(5)sys%, respectively. One-neutron branching ratio of Ga87(P1n=81(9)stat(8)sys%) and half-life of 29(4) ms were measured for the first time. The branching ratios of Ga86 were also measured to be P1n=74(2)stat(8)sys% and 16.2(9)stat(6)sys% with better precision than a previous study. The observation that P1n>P2n for both Ga86,87 was unexpected and is interpreted as a signature of dominating one-neutron emission from the two-neutron unbound excited states in Ge86,87. In order to interpret the experimental results, shell-model and Hauser-Feshbach statistical model calculations of delayed particle and γ-ray emission probabilities were performed. This model framework reproduces the experimental results. The shell model alone predicts P2n significantly larger than P1n for the Ga87 decay, and it is necessary to invoke a statistical description to successfully explain the observation that P1n>P2n. Our new results demonstrate the relevance and importance of a statistical description of neutron emission for the prediction of the decay properties of multineutron emitters and that it must be included in the r-process modeling. © 2019 American Physical Society.

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