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

R. Yokoyama; R. Grzywacz; B. C. Rasco; N. Brewer; K. P. Rykaczewski; I. Dillmann; J. L. Tain; S. Nishimura; D. S. Ahn; A. Algora; J. M. Allmond; J. Agramunt; H. Baba; S. Bae; C. G. Bruno; R. Caballero-Folch; F. Calvino; P. J. Coleman-Smith; G. Cortes; T. Davinson; C. Domingo-Pardo; A. Estrade; N. Fukuda; S. Go; C. J. Griffin; J. Ha; O. Hall; L. J. Harkness-Brennan; J. Heideman; T. Isobe; D. Kahl; M. Karny; T. Kawano; L. H. Khiem; T. T. King; G. G. Kiss; A. Korgul; S. Kubono; M. Labiche; I. Lazarus; J. Liang; J. Liu; G. Lorusso; M. Madurga; K. Matsui; K. Miernik; F. Montes; A. I. Morales; P. Morrall; N. Nepal; R. D. Page; V. H. Phong; M. Piersa; M. Prydderch; V. F.E. Pucknell; M. M. Rajabali; B. Rubio; Y. Saito; H. Sakurai; Y. Shimizu; J. Simpson; M. Singh; D. W. Stracener; T. Sumikama; R. Surman; H. Suzuki; H. Takeda; A. Tarifeño-Saldivia; S. L. Thomas; A. Tolosa-Delgado; M. Wolińska-Cichocka; P. J. Woods; X. X. Xu

doi:10.1103/PhysRevC.100.031302

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

R. Yokoyama, R. Grzywacz, B. C. Rasco, N. Brewer, K. P. Rykaczewski, I. Dillmann, J. L. Tain, S. Nishimura, D. S. Ahn, A. Algora, J. M. Allmond, J. Agramunt, H. Baba, S. Bae, C. G. Bruno, R. Caballero-Folch, F. Calvino, P. J. Coleman-Smith, G. Cortes, T. DavinsonC. Domingo-Pardo, A. Estrade, N. Fukuda, S. Go, C. J. Griffin, J. Ha, O. Hall, L. J. Harkness-Brennan, J. Heideman, T. Isobe, D. Kahl, M. Karny, T. Kawano, L. H. Khiem, T. T. King, G. G. Kiss, A. Korgul, S. Kubono, M. Labiche, I. Lazarus, J. Liang, J. Liu, G. Lorusso, M. Madurga, K. Matsui, K. Miernik, F. Montes, A. I. Morales, P. Morrall, N. Nepal, R. D. Page, V. H. Phong, M. Piersa, M. Prydderch, V. F.E. Pucknell, M. M. Rajabali, B. Rubio, Y. Saito, H. Sakurai, Y. Shimizu, J. Simpson, M. Singh, D. W. Stracener, T. Sumikama, R. Surman, H. Suzuki, H. Takeda, A. Tarifeño-Saldivia, S. L. Thomas, A. Tolosa-Delgado, M. Wolińska-Cichocka, P. J. Woods, X. X. Xu

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Abstract

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.

Original language	English
Article number	031302
Journal	Physical Review C
Volume	100
Issue number	3
DOIs	https://doi.org/10.1103/PhysRevC.100.031302
State	Published - Sep 19 2019

Funding

This experiment was performed at the RI Beam Factory operated by RIKEN Nishina Center and CNS, University of Tokyo. This research was sponsored in part by the Office of Nuclear Physics, U.S. Department of Energy under Award No. DE-FG02-96ER40983 (UTK) and DE-AC05-00OR22725 (ORNL), and by the National Nuclear Security Administration under the Stewardship Science Academic Alliances program through DOE Award No. DE-NA0002132. This work was supported by National Science Foundation under Grants No. PHY-1430152 (JINA Center for the Evolution of the Elements), No. PHY-1565546 (NSCL), and No. PHY-1714153 (Central Michigan University). This work was supported by the Polish National Science Center under Contracts No. UMO-2015/18/E/ST2/00217 and No. 2017/01/X/ST2/01144. This work was also supported by JSPS KAKENHI (Grants No. 14F04808, No. 17H06090, No. 25247045, and No. 19340074), by the UK Science and Technology Facilities Council, by NKFIH (NN128072), by Spanish Ministerio de Economia y Competitividad grants (FPA2011-06419, FPA2011-28770-C03-03, FPA2014-52823-C2-1-P, FPA2014-52823-C2-2-P, SEV-2014-0398, IJCI-2014-19172), by European Commission FP7/EURATOM Contract No. 605203, by the UK Science and Technology Facilities Council Grant No. ST/N00244X/1, by the National Research Foundation (NRF) in South Korea (No. 2016K1A3A7A09005575, No. 2015H1A2A1030275) and by the Natural Sciences and Engineering Research Council of Canada (NSERC) via the Discovery Grants SAPIN-2014-00028 and RGPAS 462257-2014. TRIUMF receives federal funding via a contribution agreement with the National Research Council of Canada. G.G.K. acknowledges support from the Janos Bolyai research fellowship of the Hungarian Academy of Sciences. M.W.-C. acknowledges support from the Polish NCN project Miniatura No. 2017/01/X/ST2/01144. T.K. carried out this work under the auspices of the National Nuclear Security Administration of the U.S. Department of Energy at Los Alamos National Laboratory under Contract No. 89233218CNA000001.

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10.1103/PhysRevC.100.031302

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Yokoyama, R., Grzywacz, R., Rasco, B. C., Brewer, N., Rykaczewski, K. P., Dillmann, I., Tain, J. L., Nishimura, S., Ahn, D. S., Algora, A., Allmond, J. M., Agramunt, J., Baba, H., Bae, S., Bruno, C. G., Caballero-Folch, R., Calvino, F., Coleman-Smith, P. J., Cortes, G., ... Xu, X. X. (2019). Strong one-neutron emission from two-neutron unbound states in β decays of the r -process nuclei Ga 86,87. Physical Review C, 100(3), Article 031302. https://doi.org/10.1103/PhysRevC.100.031302

@article{ac0dc4c4ccff4e278ea785bc2a7d754f,

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

abstract = "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.",

author = "R. Yokoyama and R. Grzywacz and Rasco, {B. C.} and N. Brewer and Rykaczewski, {K. P.} and I. Dillmann and Tain, {J. L.} and S. Nishimura and Ahn, {D. S.} and A. Algora and Allmond, {J. M.} and J. Agramunt and H. Baba and S. Bae and Bruno, {C. G.} and R. Caballero-Folch and F. Calvino and Coleman-Smith, {P. J.} and G. Cortes and T. Davinson and C. Domingo-Pardo and A. Estrade and N. Fukuda and S. Go and Griffin, {C. J.} and J. Ha and O. Hall and Harkness-Brennan, {L. J.} and J. Heideman and T. Isobe and D. Kahl and M. Karny and T. Kawano and Khiem, {L. H.} and King, {T. T.} and Kiss, {G. G.} and A. Korgul and S. Kubono and M. Labiche and I. Lazarus and J. Liang and J. Liu and G. Lorusso and M. Madurga and K. Matsui and K. Miernik and F. Montes and Morales, {A. I.} and P. Morrall and N. Nepal and Page, {R. D.} and Phong, {V. H.} and M. Piersa and M. Prydderch and Pucknell, {V. F.E.} and Rajabali, {M. M.} and B. Rubio and Y. Saito and H. Sakurai and Y. Shimizu and J. Simpson and M. Singh and Stracener, {D. W.} and T. Sumikama and R. Surman and H. Suzuki and H. Takeda and A. Tarife{\~n}o-Saldivia and Thomas, {S. L.} and A. Tolosa-Delgado and M. Woli{\'n}ska-Cichocka and Woods, {P. J.} and Xu, {X. X.}",

note = "Publisher Copyright: {\textcopyright} 2019 American Physical Society.",

year = "2019",

month = sep,

day = "19",

doi = "10.1103/PhysRevC.100.031302",

language = "English",

volume = "100",

journal = "Physical Review C",

issn = "2469-9985",

publisher = "American Physical Society",

number = "3",

}

Yokoyama, R, Grzywacz, R, Rasco, BC, Brewer, N, Rykaczewski, KP, Dillmann, I, Tain, JL, Nishimura, S, Ahn, DS, Algora, A, Allmond, JM, Agramunt, J, Baba, H, Bae, S, Bruno, CG, Caballero-Folch, R, Calvino, F, Coleman-Smith, PJ, Cortes, G, Davinson, T, Domingo-Pardo, C, Estrade, A, Fukuda, N, Go, S, Griffin, CJ, Ha, J, Hall, O, Harkness-Brennan, LJ, Heideman, J, Isobe, T, Kahl, D, Karny, M, Kawano, T, Khiem, LH, King, TT, Kiss, GG, Korgul, A, Kubono, S, Labiche, M, Lazarus, I, Liang, J, Liu, J, Lorusso, G, Madurga, M, Matsui, K, Miernik, K, Montes, F, Morales, AI, Morrall, P, Nepal, N, Page, RD, Phong, VH, Piersa, M, Prydderch, M, Pucknell, VFE, Rajabali, MM, Rubio, B, Saito, Y, Sakurai, H, Shimizu, Y, Simpson, J, Singh, M, Stracener, DW, Sumikama, T, Surman, R, Suzuki, H, Takeda, H, Tarifeño-Saldivia, A, Thomas, SL, Tolosa-Delgado, A, Wolińska-Cichocka, M, Woods, PJ & Xu, XX 2019, 'Strong one-neutron emission from two-neutron unbound states in β decays of the r -process nuclei Ga 86,87', Physical Review C, vol. 100, no. 3, 031302. https://doi.org/10.1103/PhysRevC.100.031302

TY - JOUR

T1 - Strong one-neutron emission from two-neutron unbound states in β decays of the r -process nuclei Ga 86,87

AU - Yokoyama, R.

AU - Grzywacz, R.

AU - Rasco, B. C.

AU - Brewer, N.

AU - Rykaczewski, K. P.

AU - Dillmann, I.

AU - Tain, J. L.

AU - Nishimura, S.

AU - Ahn, D. S.

AU - Algora, A.

AU - Allmond, J. M.

AU - Agramunt, J.

AU - Baba, H.

AU - Bae, S.

AU - Bruno, C. G.

AU - Caballero-Folch, R.

AU - Calvino, F.

AU - Coleman-Smith, P. J.

AU - Cortes, G.

AU - Davinson, T.

AU - Domingo-Pardo, C.

AU - Estrade, A.

AU - Fukuda, N.

AU - Go, S.

AU - Griffin, C. J.

AU - Ha, J.

AU - Hall, O.

AU - Harkness-Brennan, L. J.

AU - Heideman, J.

AU - Isobe, T.

AU - Kahl, D.

AU - Karny, M.

AU - Kawano, T.

AU - Khiem, L. H.

AU - King, T. T.

AU - Kiss, G. G.

AU - Korgul, A.

AU - Kubono, S.

AU - Labiche, M.

AU - Lazarus, I.

AU - Liang, J.

AU - Liu, J.

AU - Lorusso, G.

AU - Madurga, M.

AU - Matsui, K.

AU - Miernik, K.

AU - Montes, F.

AU - Morales, A. I.

AU - Morrall, P.

AU - Nepal, N.

AU - Page, R. D.

AU - Phong, V. H.

AU - Piersa, M.

AU - Prydderch, M.

AU - Pucknell, V. F.E.

AU - Rajabali, M. M.

AU - Rubio, B.

AU - Saito, Y.

AU - Sakurai, H.

AU - Shimizu, Y.

AU - Simpson, J.

AU - Singh, M.

AU - Stracener, D. W.

AU - Sumikama, T.

AU - Surman, R.

AU - Suzuki, H.

AU - Takeda, H.

AU - Tarifeño-Saldivia, A.

AU - Thomas, S. L.

AU - Tolosa-Delgado, A.

AU - Wolińska-Cichocka, M.

AU - Woods, P. J.

AU - Xu, X. X.

PY - 2019/9/19

Y1 - 2019/9/19

N2 - 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.

AB - 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.

UR - http://www.scopus.com/inward/record.url?scp=85072962817&partnerID=8YFLogxK

U2 - 10.1103/PhysRevC.100.031302

DO - 10.1103/PhysRevC.100.031302

M3 - Article

AN - SCOPUS:85072962817

SN - 2469-9985

VL - 100

JO - Physical Review C

JF - Physical Review C

IS - 3

M1 - 031302

ER -

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

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