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1. Shape Coexistence at Zero Spin in Ni-64 Driven by the Monopole Tensor Interaction

Author

Marginean, N, Little, D, Tsunoda, Y, Leoni, S, Janssens, RVF, Fornal, B, Otsuka, T, Michelagnoli, C, Stan, L, Crespi, FCL, Costache, C, Lica, R, Sferrazza, M, Turturica, A, Ayangeakaa, AD, Auranen, K, Barani, M, Bender, PC, Bottoni, S, Boromiza, M, Bracco, A, Calinescu, S, Campbell, CM, Carpenter, MP, Chowdhury, P, Ciemala, M, Cieplicka-Orynczak, N, Cline, D, Clisu, C, Crawford, HL, Dinescu, IE, Dudouet, J, Filipescu, D, Florea, N, Forney, AM, Fracassetti, S, Gade, A, Gheorghe, I, Hayes, AB, Harca, I, Henderson, J, Ionescu, A, Iskra, LW, Jentschel, M, Kandzia, F, Kim, YH, Kondev, FG, Korschinek, G, Koster, U, Krishichayan, Krzysiek, M, Lauritsen, T, Li, J, Marginean, R, Maugeri, EA, Mihai, C, Mihai, RE, Mitu, A, Mutti, P, Negret, A, Nita, CR, Olacel, A, Oprea, A, Pascu, S, Petrone, C, Porzio, C, Rhodes, D, Seweryniak, D, Schumann, D, Sotty, C, Stolze, SM, Suvaila, R, Toma, S, Ujeniuc, S, Walters, WB, Wu, CY, Wu, J, Zhu, S, and Ziliani, S

Subjects
Science & Technology, STATES, Physics, Physical Sciences, Physics, Multidisciplinary, TRANSITION
Abstract

The low-spin structure of the semimagic ^{64}Ni nucleus has been considerably expanded: combining four experiments, several 0^{+} and 2^{+} excited states were identified below 4.5 MeV, and their properties established. The Monte Carlo shell model accounts for the results and unveils an unexpectedly complex landscape of coexisting shapes: a prolate 0^{+} excitation is located at a surprisingly high energy (3463 keV), with a collective 2^{+} state 286 keV above it, the first such observation in Ni isotopes. The evolution in excitation energy of the prolate minimum across the neutron N=40 subshell gap highlights the impact of the monopole interaction and its variation in strength with N. ispartof: PHYSICAL REVIEW LETTERS vol:125 issue:10 ispartof: location:United States status: published

Published
2020

2. High accuracy, high resolution $^{235}$U(n,f) cross section from n_TOF (CERN) from 18 meV to 10 keV

Author

M. Mastromarco, S. Amaducci, N. Colonna, P. Finocchiaro, L. Cosentino, M. Barbagallo, O. Aberle, J. Andrzejewski, L. Audouin, M. Bacak, J. Balibrea, F. Bečvář, E. Berthoumieux, J. Billowes, D. Bosnar, A. Brown, M. Caamaño, F. Calviño, M. Calviani, D. Cano-Ott, R. Cardella, A. Casanovas, F. Cerutti, Y. H. Chen, E. Chiaveri, G. Cortés, M. A. Cortés-Giraldo, L. A. Damone, M. Diakaki, C. Domingo-Pardo, D. Diacono, R. Dressler, E. Dupont, I. Durán, B. Fernández-Domínguez, A. Ferrari, P. Ferreira, V. Furman, K. Göbel, A. R. García, A. Gawlik, S. Gilardoni, T. Glodariu, I. F. Gonçalves, E. González-Romero, E. Griesmayer, C. Guerrero, F. Gunsing, H. Harada, S. Heinitz, J. Heyse, D. G. Jenkins, E. Jericha, F. Käppeler, Y. Kadi, A. Kalamara, P. Kavrigin, A. Kimura, N. Kivel, I. Knapova, M. Kokkoris, M. Krtička, D. Kurtulgil, E. Leal-Cidoncha, C. Lederer, H. Leeb, J. Lerendegui-Marco, S. Lo Meo, S. J. Lonsdale, D. Macina, A. Manna, J. Marganiec, T. Martínez, A. Masi, C. Massimi, P. Mastinu, E. A. Maugeri, A. Mazzone, E. Mendoza, A. Mengoni, P. M. Milazzo, F. Mingrone, A. Musumarra, A. Negret, R. Nolte, A. Oprea, N. Patronis, A. Pavlik, J. Perkowski, I. Porras, J. Praena, J. M. Quesada, D. Radeck, T. Rauscher, R. Reifarth, C. Rubbia, J. A. Ryan, M. Sabaté-Gilarte, A. Saxena, P. Schillebeeckx, D. Schumann, P. Sedyshev, A. G. Smith, N. V. Sosnin, A. Stamatopoulos, G. Tagliente, J. L. Tain, A. Tarifeño-Saldivia, L. Tassan-Got, S. Valenta, G. Vannini, V. Variale, P. Vaz, A. Ventura, V. Vlachoudis, R. Vlastou, A. Wallner, S. Warren, C. Weiss, P. J. Woods, T. Wright, P. Žugec, Universitat Politècnica de Catalunya. Departament de Física, Universitat Politècnica de Catalunya. ANT - Advanced Nuclear Technologies Research Group, Mastromarco, M, Amaducci, S, Colonna, N, Finocchiaro, P, Cosentino, L, Barbagallo, M, Aberle, O, Andrzejewski, J, Audouin, L, Bacak, M, Balibrea, J, Becvar, F, Berthoumieux, E, Billowes, J, Bosnar, D, Brown, A, Caamano, M, Calvino, F, Calviani, M, Cano-Ott, D, Cardella, R, Casanovas, A, Cerutti, F, Chen, YH, Chiaveri, E, Cortes, G, Cortes-Giraldo, MA, Damone, LA, Diakaki, M, Domingo-Pardo, C, Diacono, D, Dressler, R, Dupont, E, Duran, I, Fernandez-Dominguez, B, Ferrari, A, Ferreira, P, Furman, V, Gobel, K, Garcia, AR, Gawlik, A, Gilardoni, S, Glodariu, T, Goncalves, IF, Gonzalez-Romero, E, Griesmayer, E, Guerrero, C, Gunsing, F, Harada, H, Heinitz, S, Heyse, J, Jenkins, DG, Jericha, E, Kappeler, F, Kadi, Y, Kalamara, A, Kavrigin, P, Kimura, A, Kivel, N, Knapova, I, Kokkoris, M, Krticka, M, Kurtulgil, D, Leal-Cidoncha, E, Lederer, C, Leeb, H, Lerendegui-Marco, J, LoMeo, S, Lonsdale, SJ, Macina, D, Manna, A, Marganiec, J, Martinez, T, Masi, A, Massimi, C, Mastinu, P, Maugeri, EA, Mazzone, A, Mendoza, E, Mengoni, A, Milazzo, PM, Mingrone, F, Musumarra, A, Negret, A, Nolte, R, Oprea, A, Patronis, N, Pavlik, A, Perkowski, J, Porras, I, Praena, J, Quesada, JM, Radeck, D, Rauscher, T, Reifarth, R, Rubbia, C, Ryan, JA, Sabate-Gilarte, M, Saxena, A, Schillebeeckx, P, Schumann, D, Sedyshev, P, Smith, AG, Sosnin, NV, Stamatopoulos, A, Tagliente, G, Tain, JL, Tarifeno-Saldivia, A, Tassan-Got, L, Valenta, S, Vannini, G, Variale, V, Vaz, P, Ventura, A, Vlachoudis, V, Vlastou, R, Wallner, A, Warren, S, Weiss, C, Woods, PJ, Wright, T, Zugec, P, Laboratoire de Physique des 2 Infinis Irène Joliot-Curie (IJCLab), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Institut de Recherches sur les lois Fondamentales de l'Univers (IRFU), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, and n_TOF

Subjects
Neutrons, Nuclear and High Energy Physics, Fission, Energies [Àrees temàtiques de la UPC], Nuclear physics, 235U, fission, cross section, n_TOF, CERN, [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], Espectroscòpia de ressonància magnètica nuclear, Resonance, n_TOF, cross section, 235U, CERN, Física nuclear, Nuclear Physics - Experiment, Nuclear Experiment, Nuclear magnetic resonance spectroscopy, Neutron energy
Abstract

The 235U(n,f) cross section was measured in a wide energy range (18 meV–170 keV) at the n_TOF facility at CERN, relative to 6Li(n,t) and 10B(n,α) standard reactions, with high resolution and accuracy, with a setup based on a stack of six samples and six silicon detectors placed in the neutron beam. In this paper we report on the results in the region between 18 meV and 10 keV neutron energy. A resonance analysis has been performed up to 200 eV, with the code SAMMY. The resulting fission kernels are compared with the ones extracted on the basis of the resonance parameters of the most recent major evaluated data libraries.Acomparison of the n_TOF datawith the evaluated cross sections is also performed from thermal to 10 keV neutron energy for the energy-averaged cross section in energy groups of suitably chosen width. A good agreement, within 0.5%, is found on average between the new results and the latest evaluated data files ENDF/B-VIII.0 and JEFF-3.3, as well as with respect to the broad group average fission cross section established in the framework of the standard working group of IAEA (the so-called reference file). However, some discrepancies, of up to 4%, are still present in some specific energy regions. The newdataset here presented, characterized by a unique combination of high resolution and accuracy, low background and wide energy range, can help to improve the evaluations from the Resolved Resonance Region up to 10 keV, also reducing the uncertainties that affect this region., CERN (European Organization for Nuclear Research)

Published
2022

3. Shedding Light on the Origin of ^{204}Pb, the Heaviest s-Process-Only Isotope in the Solar System.

Author

Casanovas-Hoste A, Domingo-Pardo C, Lerendegui-Marco J, Guerrero C, Tarifeño-Saldivia A, Krtička M, Pignatari M, Calviño F, Schumann D, Heinitz S, Dressler R, Köster U, Aberle O, Andrzejewski J, Audouin L, Bécares V, Bacak M, Balibrea-Correa J, Barbagallo M, Barros S, Bečvář F, Beinrucker C, Berthoumieux E, Billowes J, Bosnar D, Brugger M, Caamaño M, Calviani M, Cano-Ott D, Cardella R, Castelluccio DM, Cerutti F, Chen YH, Chiaveri E, Colonna N, Cortés G, Cortés-Giraldo MA, Cosentino L, Damone LA, Diakaki M, Dupont E, Durán I, Fernández-Domínguez B, Ferrari A, Ferreira P, Finocchiaro P, Furman V, Göbel K, García AR, Gawlik-Ramięga A, Glodariu T, Gonçalves IF, González-Romero E, Goverdovski A, Griesmayer E, Gunsing F, Harada H, Heftrich T, Heyse J, Jenkins DG, Jericha E, Käppeler F, Kadi Y, Katabuchi T, Kavrigin P, Ketlerov V, Khryachkov V, Kimura A, Kivel N, Kokkoris M, Leal-Cidoncha E, Lederer-Woods C, Leeb H, Lo Meo S, Lonsdale SJ, Losito R, Macina D, Marganiec J, Martínez T, Massimi C, Mastinu P, Mastromarco M, Matteucci F, Maugeri EA, Mendoza E, Mengoni A, Milazzo PM, Mingrone F, Mirea M, Montesano S, Musumarra A, Nolte R, Oprea A, Patronis N, Pavlik A, Perkowski J, Porras I, Praena J, Quesada JM, Rajeev K, Rauscher T, Reifarth R, Riego-Perez A, Romanets Y, Rout PC, Rubbia C, Ryan JA, Sabaté-Gilarte M, Saxena A, Schillebeeckx P, Schmidt S, Sedyshev P, Smith AG, Stamatopoulos A, Tagliente G, Tain JL, Tassan-Got L, Tsinganis A, Valenta S, Vannini G, Variale V, Vaz P, Ventura A, Vlachoudis V, Vlastou R, Wallner A, Warren S, Weigand M, Weiss C, Wolf C, Woods PJ, Wright T, and Žugec P

Abstract

Asymptotic giant branch stars are responsible for the production of most of the heavy isotopes beyond Sr observed in the solar system. Among them, isotopes shielded from the r-process contribution by their stable isobars are defined as s-only nuclei. For a long time the abundance of ^{204}Pb, the heaviest s-only isotope, has been a topic of debate because state-of-the-art stellar models appeared to systematically underestimate its solar abundance. Besides the impact of uncertainties from stellar models and galactic chemical evolution simulations, this discrepancy was further obscured by rather divergent theoretical estimates for the neutron capture cross section of its radioactive precursor in the neutron-capture flow, ^{204}Tl (t_{1/2}=3.78  yr), and by the lack of experimental data on this reaction. We present the first ever neutron capture measurement on ^{204}Tl, conducted at the CERN neutron time-of-flight facility n_TOF, employing a sample of only 9 mg of ^{204}Tl produced at the Institute Laue Langevin high flux reactor. By complementing our new results with semiempirical calculations we obtained, at the s-process temperatures of kT≈8  keV and kT≈30  keV, Maxwellian-averaged cross sections (MACS) of 580(168) mb and 260(90) mb, respectively. These figures are about 3% lower and 20% higher than the corresponding values widely used in astrophysical calculations, which were based only on theoretical calculations. By using the new ^{204}Tl MACS, the uncertainty arising from the ^{204}Tl(n,γ) cross section on the s-process abundance of ^{204}Pb has been reduced from ∼30% down to +8%/-6%, and the s-process calculations are in agreement with the latest solar system abundance of ^{204}Pb reported by K. Lodders in 2021.

Published
2024
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4. Measurement of the ^{140}Ce(n,γ) Cross Section at n_TOF and Its Astrophysical Implications for the Chemical Evolution of the Universe.

Author

Amaducci S, Colonna N, Cosentino L, Cristallo S, Finocchiaro P, Krtička M, Massimi C, Mastromarco M, Mazzone A, Maugeri EA, Mengoni A, Roederer IU, Straniero O, Valenta S, Vescovi D, Aberle O, Alcayne V, Andrzejewski J, Audouin L, Babiano-Suarez V, Bacak M, Barbagallo M, Bennett S, Berthoumieux E, Billowes J, Bosnar D, Brown A, Busso M, Caamaño M, Caballero-Ontanaya L, Calviño F, Calviani M, Cano-Ott D, Casanovas A, Cerutti F, Chiaveri E, Cortés G, Cortés-Giraldo MA, Damone LA, Davies PJ, Diakaki M, Dietz M, Domingo-Pardo C, Dressler R, Ducasse Q, Dupont E, Durán I, Eleme Z, Fernández-Domínguez B, Ferrari A, Furman V, Göbel K, Garg R, Gawlik-Ramięga A, Gilardoni S, Gonçalves IF, González-Romero E, Guerrero C, Gunsing F, Harada H, Heinitz S, Heyse J, Jenkins DG, Junghans A, Käppeler F, Kadi Y, Kimura A, Knapová I, Kokkoris M, Kopatch Y, Kurtulgil D, Ladarescu I, Lederer-Woods C, Leeb H, Lerendegui-Marco J, Lonsdale SJ, Macina D, Manna A, Martínez T, Masi A, Mastinu P, Mendoza E, Michalopoulou V, Milazzo PM, Mingrone F, Moreno-Soto J, Musumarra A, Negret A, Nolte R, Ogállar F, Oprea A, Patronis N, Pavlik A, Perkowski J, Petrone C, Piersanti L, Pirovano E, Porras I, Praena J, Quesada JM, Ramos-Doval D, Rauscher T, Reifarth R, Rochman D, Rubbia C, Sabaté-Gilarte M, Saxena A, Schillebeeckx P, Schumann D, Sekhar A, Smith AG, Sosnin NV, Sprung P, Stamatopoulos A, Tagliente G, Tain JL, Tarifeño-Saldivia A, Tassan-Got L, Thomas T, Torres-Sánchez P, Tsinganis A, Ulrich J, Urlass S, Vannini G, Variale V, Vaz P, Ventura A, Vlachoudis V, Vlastou R, Wallner A, Woods PJ, Wright T, and Žugec P

Abstract

^{140}Ce(n,γ) is a key reaction for slow neutron-capture (s-process) nucleosynthesis due to being a bottleneck in the reaction flow. For this reason, it was measured with high accuracy (uncertainty ≈5%) at the n_TOF facility, with an unprecedented combination of a high purity sample and low neutron-sensitivity detectors. The measured Maxwellian averaged cross section is up to 40% higher than previously accepted values. Stellar model calculations indicate a reduction around 20% of the s-process contribution to the Galactic cerium abundance and smaller sizeable differences for most of the heavier elements. No variations are found in the nucleosynthesis from massive stars.

Published
2024
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5. Measurement of the 171 Tm beta spectrum.

Author

Juget F, van Dijk M, Maugeri EA, Schumann MD, Heinitz S, Boyarsky A, Köster U, Shchutska L, and Bailat C

Abstract

The beta spectrum of the main transition of the β - decay of 171 Tm was measured using a double focalizing spectrometer. The instrument was lately improved in order to reduce its low energy threshold to 34 keV. We used the spectrometer to measure the beta spectrum end-point energy of the main transition of 171 Tm decay using the Kurie plot formalism. We report a new value of 97.60(38) keV, which is in agreement with previous measurements. In addition, the spectrum shape was compared with the ξ-approximation calculation where the shape factor is equal to 1 and good agreement was found between the theory and the measurement at the 1% level., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Published
2023
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6. Evidence of a Near-Threshold Resonance in ^{11}B Relevant to the β-Delayed Proton Emission of ^{11}Be.

Author

Ayyad Y, Mittig W, Tang T, Olaizola B, Potel G, Rijal N, Watwood N, Alvarez-Pol H, Bazin D, Caamaño M, Chen J, Cortesi M, Fernández-Domínguez B, Giraud S, Gueye P, Heinitz S, Jain R, Kay BP, Maugeri EA, Monteagudo B, Ndayisabye F, Paneru SN, Pereira J, Rubino E, Santamaria C, Schumann D, Surbrook J, Wagner L, Zamora JC, and Zelevinsky V

Abstract

A narrow near-threshold proton-emitting resonance (E_{x}=11.4  MeV, J^{π}=1/2^{+}, and Γ_{p}=4.4  keV) was directly observed in ^{11}B via proton resonance scattering. This resonance was previously inferred in the β-delayed proton emission of the neutron halo nucleus ^{11}Be. The good agreement between both experimental results serves as a ground to confirm the existence of such exotic decay and the particular behavior of weakly bound nuclei coupled to the continuum. R-matrix analysis shows a sizable partial decay width for both, proton and α (Γ_{α}=11  keV) emission channels.

Published
2022
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7. 74 Ge( n , γ ) cross section below 70 keV measured at n_TOF CERN.

Author

Lederer-Woods C, Aberle O, Andrzejewski J, Audouin L, Bécares V, Bacak M, Balibrea J, Barbagallo M, Barros S, Battino U, Bečvář F, Beinrucker C, Berthoumieux E, Billowes J, Bosnar D, Brugger M, Caamaño M, Calviño F, Calviani M, Cano-Ott D, Cardella R, Casanovas A, Castelluccio DM, Cerutti F, Chen YH, Chiaveri E, Colonna N, Cortés G, Cortés-Giraldo MA, Cosentino L, Damone LA, Diakaki M, Domingo-Pardo C, Dressler R, Dupont E, Durán I, Fernández-Domínguez B, Ferrari A, Ferreira P, Finocchiaro P, Furman V, Göbel K, García AR, Gawlik-Ramięga A, Glodariu T, Gonçalves IF, González-Romero E, Goverdovski A, Griesmayer E, Guerrero C, Gunsing F, Harada H, Heftrich T, Heinitz S, Heyse J, Jenkins DG, Jericha E, Käppeler F, Kadi Y, Katabuchi T, Kavrigin P, Ketlerov V, Khryachkov V, Kimura A, Kivel N, Kokkoris M, Krtička M, Leal-Cidoncha E, Leeb H, Lerendegui-Marco J, Meo SL, Lonsdale SJ, Losito R, Macina D, Marganiec J, Martínez T, Massimi C, Mastinu P, Mastromarco M, Matteucci F, Maugeri EA, Mendoza E, Mengoni A, Milazzo PM, Mingrone F, Mirea M, Montesano S, Musumarra A, Nolte R, Oprea A, Patronis N, Pavlik A, Perkowski J, Porras I, Praena J, Quesada JM, Rajeev K, Rauscher T, Reifarth R, Riego-Perez A, Rout PC, Rubbia C, Ryan JA, Sabaté-Gilarte M, Saxena A, Schillebeeckx P, Schmidt S, Schumann D, Sedyshev P, Smith AG, Stamatopoulos A, Tagliente G, Tain JL, Tarifeño-Saldivia A, Tassan-Got L, Tsinganis A, Valenta S, Vannini G, Variale V, Vaz P, Ventura A, Vlachoudis V, Vlastou R, Wallner A, Warren S, Weigand M, Weiss C, Wolf C, Woods PJ, Wright T, and Žugec P

Abstract

Neutron capture reaction cross sections on 74 Ge are of importance to determine 74 Ge production during the astrophysical slow neutron capture process. We present new resonance data on 74 Ge( n , γ ) reactions below 70 keV neutron energy. We calculate Maxwellian averaged cross sections, combining our data below 70 keV with evaluated cross sections at higher neutron energies. Our stellar cross sections are in agreement with a previous activation measurement performed at Forschungszentrum Karlsruhe by Marganiec et al., once their data has been re-normalised to account for an update in the reference cross section used in that experiment., (© The Author(s) 2022.)

Published
2022
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8. Neutron Capture on the s-Process Branching Point ^{171}Tm via Time-of-Flight and Activation.

Author

Guerrero C, Lerendegui-Marco J, Paul M, Tessler M, Heinitz S, Domingo-Pardo C, Cristallo S, Dressler R, Halfon S, Kivel N, Köster U, Maugeri EA, Palchan-Hazan T, Quesada JM, Rochman D, Schumann D, Weissman L, Aberle O, Amaducci S, Andrzejewski J, Audouin L, Bécares V, Bacak M, Balibrea J, Barak A, Barbagallo M, Barros S, Bečvář F, Beinrucker C, Berkovits D, Berthoumieux E, Billowes J, Bosnar D, Brugger M, Buzaglo Y, Caamaño M, Calviño F, Calviani M, Cano-Ott D, Cardella R, Casanovas A, Castelluccio DM, Cerutti F, Chen YH, Chiaveri E, Colonna N, Cortés G, Cortés-Giraldo MA, Cosentino L, Dafna H, Damone A, Diakaki M, Dietz M, Dupont E, Durán I, Eisen Y, Fernández-Domínguez B, Ferrari A, Ferreira P, Finocchiaro P, Furman V, Göbel K, García AR, Gawlik A, Glodariu T, Gonçalves IF, González-Romero E, Goverdovski A, Griesmayer E, Gunsing F, Harada H, Heftrich T, Heyse J, Hirsh T, Jenkins DG, Jericha E, Käppeler F, Kadi Y, Kaizer B, Katabuchi T, Kavrigin P, Ketlerov V, Khryachkov V, Kijel D, Kimura A, Kokkoris M, Kriesel A, Krtička M, Leal-Cidoncha E, Lederer-Woods C, Leeb H, Lo Meo S, Lonsdale SJ, Losito R, Macina D, Manna A, Marganiec J, Martínez T, Massimi C, Mastinu P, Mastromarco M, Matteucci F, Mendoza E, Mengoni A, Milazzo PM, Millán-Callado MA, Mingrone F, Mirea M, Montesano S, Musumarra A, Nolte R, Oprea A, Patronis N, Pavlik A, Perkowski J, Piersanti L, Porras I, Praena J, Rajeev K, Rauscher T, Reifarth R, Rodríguez-González T, Rout PC, Rubbia C, Ryan JA, Sabaté-Gilarte M, Saxena A, Schillebeeckx P, Schmidt S, Shor A, Sedyshev P, Smith AG, Stamatopoulos A, Tagliente G, Tain JL, Tarifeño-Saldivia A, Tassan-Got L, Tsinganis A, Valenta S, Vannini G, Variale V, Vaz P, Ventura A, Vlachoudis V, Vlastou R, Wallner A, Warren S, Weigand M, Weiss C, Wolf C, Woods PJ, Wright T, and Žugec P

Abstract

The neutron capture cross sections of several unstable nuclides acting as branching points in the s process are crucial for stellar nucleosynthesis studies. The unstable ^{171}Tm (t_{1/2}=1.92  yr) is part of the branching around mass A∼170 but its neutron capture cross section as a function of the neutron energy is not known to date. In this work, following the production for the first time of more than 5 mg of ^{171}Tm at the high-flux reactor Institut Laue-Langevin in France, a sample was produced at the Paul Scherrer Institute in Switzerland. Two complementary experiments were carried out at the neutron time-of-flight facility (n_TOF) at CERN in Switzerland and at the SARAF liquid lithium target facility at Soreq Nuclear Research Center in Israel by time of flight and activation, respectively. The result of the time-of-flight experiment consists of the first ever set of resonance parameters and the corresponding average resonance parameters, allowing us to make an estimation of the Maxwellian-averaged cross sections (MACS) by extrapolation. The activation measurement provides a direct and more precise measurement of the MACS at 30 keV: 384(40) mb, with which the estimation from the n_TOF data agree at the limit of 1 standard deviation. This value is 2.6 times lower than the JEFF-3.3 and ENDF/B-VIII evaluations, 25% lower than that of the Bao et al. compilation, and 1.6 times larger than the value recommended in the KADoNiS (v1) database, based on the only previous experiment. Our result affects the nucleosynthesis at the A∼170 branching, namely, the ^{171}Yb abundance increases in the material lost by asymptotic giant branch stars, providing a better match to the available pre-solar SiC grain measurements compared to the calculations based on the current JEFF-3.3 model-based evaluation.

Published
2020
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9. Shape Coexistence at Zero Spin in ^{64}Ni Driven by the Monopole Tensor Interaction.

Author

Mărginean N, Little D, Tsunoda Y, Leoni S, Janssens RVF, Fornal B, Otsuka T, Michelagnoli C, Stan L, Crespi FCL, Costache C, Lica R, Sferrazza M, Turturica A, Ayangeakaa AD, Auranen K, Barani M, Bender PC, Bottoni S, Boromiza M, Bracco A, Călinescu S, Campbell CM, Carpenter MP, Chowdhury P, Ciemała M, Cieplicka-Oryǹczak N, Cline D, Clisu C, Crawford HL, Dinescu IE, Dudouet J, Filipescu D, Florea N, Forney AM, Fracassetti S, Gade A, Gheorghe I, Hayes AB, Harca I, Henderson J, Ionescu A, Iskra ŁW, Jentschel M, Kandzia F, Kim YH, Kondev FG, Korschinek G, Köster U, Krishichayan, Krzysiek M, Lauritsen T, Li J, Mărginean R, Maugeri EA, Mihai C, Mihai RE, Mitu A, Mutti P, Negret A, Niţă CR, Olăcel A, Oprea A, Pascu S, Petrone C, Porzio C, Rhodes D, Seweryniak D, Schumann D, Sotty C, Stolze SM, Şuvăilă R, Toma S, Ujeniuc S, Walters WB, Wu CY, Wu J, Zhu S, and Ziliani S

Abstract

The low-spin structure of the semimagic ^{64}Ni nucleus has been considerably expanded: combining four experiments, several 0^{+} and 2^{+} excited states were identified below 4.5 MeV, and their properties established. The Monte Carlo shell model accounts for the results and unveils an unexpectedly complex landscape of coexisting shapes: a prolate 0^{+} excitation is located at a surprisingly high energy (3463 keV), with a collective 2^{+} state 286 keV above it, the first such observation in Ni isotopes. The evolution in excitation energy of the prolate minimum across the neutron N=40 subshell gap highlights the impact of the monopole interaction and its variation in strength with N.

Published
2020
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