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Caballero-Folch, R. et al; Agramunt, J.; Tain, J.L.; Algora, A.; Domingo-Pardo, C.; Guadilla, V.; Montaner-Piza, A.; Orrigo, S.E.A.; Rubio, B.; Tarifeño-Saldivia, A.; Tolosa-Delgado, A. |
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Title |
First determination of beta-delayed multiple neutron emission beyond A=100 through direct neutron measurement: The P-2n value of Sb-136 |
Type |
Journal Article |
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Year |
2018 |
Publication |
Physical Review C |
Abbreviated Journal |
Phys. Rev. C |
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Volume |
98 |
Issue |
3 |
Pages |
034310 - 10pp |
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Abstract |
Background: beta-delayed multiple neutron emission has been observed for some nuclei with A <= 100 being the Rb-100 the heaviest beta 2n emitter measured to date. So far only 25 P-2n values have been determined for the approximate to 300 nuclei that may decay in this way. Accordingly it is of interest to measure P-2n values for the other possible multiple neutron emitters throughout the chart of the nuclides. It is of particular interest to make such a measurement for nuclei with A > 100 to test the predictions of theoretical models and simulation tools for the decays of heavy nuclei in the region of very neutron-rich nuclei. In addition the decay properties of these nuclei are fundamental for the understanding of astrophysical nucleosynthesis processes such as the r-process and safety inputs for nuclear reactors. Purpose: To determine for the first time the two-neutron branching ratio the P-2n value for Sb-136 through a direct neutron measurement and to provide precise P-1n values for Sb-136 and Te-136. Method: A pure beam of each isotope of interest was provided by the JYFLTRAP Penning trap at the Ion Guide Isotope Separator On-Line (IGISOL) facility of the University of Jyvaskyla Finland. The purified ions were implanted into a moving tape at the end of the beam line. The detection setup consisted of a plastic scintillator placed right behind the implantation point after the tape to register the beta decays and the BELEN detector based on neutron counters embedded in a polyethylene matrix. The analysis was based on the study of the beta- and neutron-growth-and-decay curves and the beta-one-neutron and beta-two-neutron time correlations which allowed us the determination of the neutron branching ratios. Results: The P-2n value of Sb-136 was found to be 0.14(3)% and the measured P-1n values for Sb-136 and Te-136 were found to be 32.2(15)% and 1.47(6)% respectively. Conclusions: The measured P-2n value is a factor 44 smaller than predicted by the finite-range droplet model plus the quasiparticle random-phase approximation (FRDM+QRPA) model used for r-process calculations. |
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[Caballero-Folch, R.; Dillmann, I] TRIUMF, Vancouver, BC V6T 2A3, Canada, Email: rcaballero-folch@triumf.ca |
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Amer Physical Soc |
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English |
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ISSN |
2469-9985 |
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Conference |
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Notes |
WOS:000444207600003 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
3728 |
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Author |
Delafosse, C. et al; Gadea, A.; Perez-Vidal, R.M.; Domingo-Pardo, C. |
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Title |
Pseudospin Symmetry and Microscopic Origin of Shape Coexistence in the Ni-78 Region: A Hint from Lifetime Measurements |
Type |
Journal Article |
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Year |
2018 |
Publication |
Physical Review Letters |
Abbreviated Journal |
Phys. Rev. Lett. |
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Volume |
121 |
Issue |
19 |
Pages |
192502 - 7pp |
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Abstract |
Lifetime measurements of excited states of the light N = 52 isotones Kr-88, Se-86, and Ge-84 have been performed, using the recoil distance Doppler shift method and VAMOS and AGATA spectrometers for particle identification and gamma spectroscopy, respectively. The reduced electric quadrupole transition probabilities B(E2; 2(+)-> 0(+)) and B(E2; 4(+)-> 2(+)) were obtained for the first time for the hard-to-reach 84Ge. While the B(E2; 2(+)-> 0(+) ) values of Kr-88, Se-86 saturate the maximum quadrupole collectivity offered by the natural valence (3s, 2d, 1g(7/2), 1h(11/2)) space of an inert Ni-78 core, the value obtained for Ge-84 largely exceeds it, suggesting that shape coexistence phenomena, previously reported at N less than or similar to 49, extend beyond N = 50. The onset of collectivity at Z = 32 is understood as due to a pseudo-SU(3) organization of the proton single-particle sequence reflecting a clear manifestation of pseudospin symmetry. It is realized that the latter provides actually reliable guidance for understanding the observed proton and neutron single particle structure in the whole medium-mass region, from Ni to Sn, pointing towards the important role of the isovector-vector rho field in shell-structure evolution. |
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[Delafosse, C.; Verney, D.; Marevic, P.; Gottardo, A.; Babo, M.; Franchoo, S.; Ibrahim, F.; Matea, I; Olivier, L.; Portail, C.; Stefan, I] Univ Paris Saclay, Univ Paris Sud, CNRS IN2P3, Inst Phys Nucl, F-91406 Orsay, France, Email: verney@ipno.in2p3.fr |
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Amer Physical Soc |
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English |
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ISSN |
0031-9007 |
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Notes |
WOS:000449791600008 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
3800 |
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Author |
Biswas, S. et al; Perez-Vidal, R.M.; Domingo-Pardo, C. |
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Title |
Effects of one valence proton on seniority and angular momentum of neutrons in neutron-rich(51)( 122-)(131)Sb isotopes |
Type |
Journal Article |
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Year |
2019 |
Publication |
Physical Review C |
Abbreviated Journal |
Phys. Rev. C |
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Volume |
99 |
Issue |
6 |
Pages |
064302 - 21pp |
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Abstract |
Background: Levels fulfilling the seniority scheme and relevant isomers are commonly observed features in semimagic nuclei; for example, in Sn isotopes (Z = 50). Seniority isomers in Sn, with dominantly pure neutron configurations, directly probe the underlying neutron-neutron (vv) interaction. Furthermore, an addition of a valence proton particle or hole, through neutron-proton (v pi) interaction, affects the neutron seniority as well as the angular momentum. Purpose: Benchmark the reproducibility of the experimental observables, like the excitation energies (E-x) and the reduced electric-quadrupole transition probabilities [B(E2)], with the results obtained from shell-model interactions for neutron-rich Sn and Sb isotopes with N < 82. Study the sensitivity of the aforementioned experimental observables to the model interaction components. Furthermore, explore from a microscopic point of view the structural similarity between the isomers in Sn and Sb, and thus the importance of the valence proton. Methods: The neutron-rich Sb122-131 isotopes were produced as fission fragments in the reaction Be-9(U-238, f) with 6.2 MeV/u beam energy. A unique setup, consisting of AGATA, VAMOS++, and EXOGAM detectors, was used which enabled the prompt-delayed gamma-ray spectroscopy of fission fragments in the time range of 100 ns to 200 μs. Results: New isomers and prompt and delayed transitions were established in the even-A Sb122-131 isotopes. In the odd-A Sb122-131 isotopes, new prompt and delayed gamma-ray transitions were identified, in addition to the confirmation of the previously known isomers. The half-lives of the isomeric states and the B(E2) transition probabilities of the observed transitions depopulating these isomers were extracted. Conclusions: The experimental data was compared with the theoretical results obtained in the framework of large-scale shell-model (LSSM) calculations in a restricted model space. Modifications of several components of the shell-model interaction were introduced to obtain a consistent agreement with the excitation energies and the B(E2) transition probabilities in neutron-rich Sn and Sb isotopes. The isomeric configurations in Sn and Sb were found to be relatively pure. Furthermore, the calculations revealed that the presence of a single valence proton, mainly in the g(7/2) orbital in Sb isotopes, leads to significant mixing (due to the v pi interaction) of (i) the neutron seniorities (upsilon(v)) and (ii) the neutron angular momentum (I-v). The above features have a weak impact on the excitation energies, but have an important impact on the B(E2) transition probabilities. In addition, a constancy of the relative excitation energies irrespective of neutron seniority and neutron number in Sn and Sb was observed. |
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Address |
[Biswas, S.; Lemasson, A.; Rejmund, M.; Navin, A.; Kim, Y. H.; Michelagnoli, C.; Clement, E.; de France, G.; Fremont, G.; Goupil, J.; Jacquot, B.; Li, H. J.; Menager, A.; More, V; Ropert, J.; Lefevre, A.; Saillant, F.] CNRS, GANIL, CEA, IN2P3,DRF, Bd Henri Becquerel,BP 55027, F-14076 Caen 5, France, Email: biswas@ganil.fr; |
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Amer Physical Soc |
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English |
Summary Language |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
2469-9985 |
ISBN |
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Conference |
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Notes |
WOS:000470856500002 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
4051 |
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Author |
Phong, V.H. et al; Agramunt, J.; Algora, A.; Domingo-Pardo, C.; Morales, A.I.; Tain, J.L.; Tarifeño-Saldivia, A.; Tolosa-Delgado, A. |
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Title |
Observation of a μs isomer in In-134(49)85: Proton-neutron coupling “southeast” of Sn-132(50)82 |
Type |
Journal Article |
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Year |
2019 |
Publication |
Physical Review C |
Abbreviated Journal |
Phys. Rev. C |
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Volume |
100 |
Issue |
1 |
Pages |
011302 - 6pp |
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Abstract |
We report on the observation of a microsecond isomeric state in the single-proton-hole, three-neutron-particle nucleus In-134. The nuclei of interest were produced by in-flight fission of a U-238 beam at the Radioactive Isotope Beam Factory at RIKEN. The isomer depopulates through a gamma ray of energy 56.7(1) keV and with a half-life of T-1/2 = 3.5(4) μs. Based on the comparison with shell-model calculations, we interpret the isomer as the I-pi = 5(-) member of the pi 0g(9/2)(-1) circle times nu 1f(7/2)(3) multiplet, decaying to the I-pi = 7(-) ground state with a reduced-transition probability of B(E2; 5(-) -> 7(-)) = 0.53(6) W.u. Observation of this isomer, and lack of evidence in the current work for a I-pi = 5(-) isomer decay in In-132, provides a benchmark of the proton-neutron interaction in the region of the nuclear chart “southeast” of Sn-132, where experimental information on excited states is sparse. |
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[Phong, V. H.; Lorusso, G.; Liu, J.; Matsui, K.; Nishimura, S.; Ahn, D. S.; Baba, H.; Go, S.; Isobe, T.; Kiss, G.; Kubono, S.; Sakurai, H.; Shimizu, Y.; Sumikama, T.; Suzuki, H.; Takeda, H.] RIKEN, RIKEN Nishina Ctr, 2-1 Hirosawa, Wako, Saitama 3510198, Japan, Email: giuseppe.lorusso@npl.co.uk |
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Publisher |
Amer Physical Soc |
Place of Publication |
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English |
Summary Language |
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Original Title |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
2469-9985 |
ISBN |
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Conference |
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Notes |
WOS:000477895400001 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
4080 |
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Author |
Yokoyama, R. et al; Tain, J.L.; Algora, A.; Agramunt, J.; Domingo-Pardo, C.; Morales, A.I.; Rubio, B.; Tolosa-Delgado, A. |
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Title |
Strong one-neutron emission from two-neutron unbound states in beta decays of the r-process nuclei Ga-86,Ga-87 |
Type |
Journal Article |
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Year |
2019 |
Publication |
Physical Review C |
Abbreviated Journal |
Phys. Rev. C |
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Volume |
100 |
Issue |
3 |
Pages |
031302 - 6pp |
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Keywords |
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Abstract |
beta-delayed one-neutron and two-neutron branching ratios (P-1n and P-2n) 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 He-3 neutron counters (BRIKEN). Two-neutron emission was observed in the decay of Ga-84,Ga-85,Ga-87 for the first time and the branching ratios were measured to be P-2n = 1.6(2)%, 1.3(2)%, and 10.2(28)(stat)(5)(sys)%, respectively. One-neutron branching ratio of Ga-87 (P-1n = 81(9)(stat)(8)(sys)%) and half-life of 29(4) ms were measured for the first time. The branching ratios of Ga-86 were also measured to be P-1n = 74(2)(stat)(8)(sys)% and 16.2(9)(stat)(6)(sys)% with better precision than a previous study. The observation that P-1n > P-2n for both Ga-86,Ga-87 was unexpected and is interpreted as a signature of dominating one-neutron emission from the two-neutron unbound excited states in Ge-86,Ge-87. In order to interpret the experimental results, shell-model and Hauser-Feshbach statistical model calculations of delayed particle and gamma-ray emission probabilities were performed. This model framework reproduces the experimental results. The shell model alone predicts P-2n significantly larger than P-1n for the Ga-87 decay, and it is necessary to invoke a statistical description to successfully explain the observation that P-1n > P-2n. 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. |
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Address |
[Yokoyama, R.; Grzywacz, R.; Rasco, B. C.; Brewer, N.; Heideman, J.; King, T. T.; Madurga, M.; Singh, M.] Univ Tennessee, Dept Phys & Astron, Knoxville, TN 37996 USA, Email: ryokoyam@utk.edu |
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Publisher |
Amer Physical Soc |
Place of Publication |
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Language |
English |
Summary Language |
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Original Title |
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Series Editor |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
2469-9985 |
ISBN |
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Expedition |
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Conference |
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Notes |
WOS:000486641000001 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
4145 |
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