Author: "Simpson, G.S." - Searchworks@Jio Institute Digital Library Search Results

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210 results on '"Simpson, G.S."'

1. Test of the SO(6) selection rule in 196Pt using cold-neutron capture

Author: Jolie, J., Régis, J.-M., Wilmsen, D., Saed-Samii, N., Pfeiffer, M., Warr, N., Blanc, A., Jentschel, M., Köster, U., Mutti, P., Soldner, T., Simpson, G.S., De France, G., Urban, W., Drouet, F., Vancraeyenest, A., Bruce, A.M., Roberts, O.J., Fraile, L.M., Paziy, V., Ignatov, A., Kröll, Th., Ivanova, D., Kisyov, S., Lalkovski, S., Podolyak, Zs., Regan, P.H., Wilson, E., Korten, W., Ur, C.A., Lica, R., and Marginean, N.
Published: 2015
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2. Germanium-gated γ–γ fast timing of excited states in fission fragments using the EXILL&FATIMA spectrometer

Author: Régis, J.-M., Simpson, G.S., Blanc, A., de France, G., Jentschel, M., Köster, U., Mutti, P., Paziy, V., Saed-Samii, N., Soldner, T., Ur, C.A., Urban, W., Bruce, A.M., Drouet, F., Fraile, L.M., Ilieva, S., Jolie, J., Korten, W., Kröll, T., Lalkovski, S., Mach, H., Mărginean, N., Pascovici, G., Podolyak, Zs., Regan, P.H., Roberts, O.J., Smith, J.F., Townsley, C., Vancraeyenest, A., and Warr, N.
Published: 2014
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3. The Collinear Resonance Ionization Spectroscopy (CRIS) experimental setup at CERN-ISOLDE

Author: Cocolios, T.E., Al Suradi, H.H., Billowes, J., Budinčević, I., de Groote, R.P., De Schepper, S., Fedosseev, V.N., Flanagan, K.T., Franchoo, S., Garcia Ruiz, R.F., Heylen, H., Le Blanc, F., Lynch, K.M., Marsh, B.A., Mason, P.J.R., Neyens, G., Papuga, J., Procter, T.J., Rajabali, M.M., Rossel, R.E., Rothe, S., Simpson, G.S., Smith, A.J., Strashnov, I., Stroke, H.H., Verney, D., Walker, P.M., Wendt, K.D.A., and Wood, R.T.
Published: 2013
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4. Shape dynamics in neutron-rich Kr isotopes: Coulomb excitation of 92Kr, 94Kr and 96Kr

Author: Albers, M., Nomura, K., Warr, N., Blazhev, A., Jolie, J., Mücher, D., Bastin, B., Bauer, C., Bernards, C., Bettermann, L., Bildstein, V., Butterworth, J., Cappellazzo, M., Cederkäll, J., Cline, D., Darby, I., Das Gupta, S., Daugas, J.M., Davinson, T., De Witte, H., Diriken, J., Filipescu, D., Fiori, E., Fransen, C., Gaffney, L.P., Georgiev, G., Gernhäuser, R., Hackstein, M., Heinze, S., Hess, H., Huyse, M., Jenkins, D., Konki, J., Kowalczyk, M., Kröll, T., Krücken, R., Litzinger, J., Lutter, R., Marginean, N., Mihai, C., Moschner, K., Napiorkowski, P., Nara Singh, B.S., Nowak, K., Pakarinen, J., Pfeiffer, M., Radeck, D., Reiter, P., Rigby, S., Robledo, L.M., Rodríguez-Guzmán, R., Rudigier, M., Scheck, M., Seidlitz, M., Siebeck, B., Simpson, G.S., Thöle, P., Thomas, T., Van de Walle, J., Van Duppen, P., Vermeulen, M., Voulot, D., Wadsworth, R., Wenander, F., Wimmer, K., Zell, K.O., and Zielinska, M.
Published: 2013
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5. Lifetime measurement in neutron-rich A~100 nuclei

Author: Ansari S., Régis J-M., Jolie J., Saed-Samii N., Warr N., Korten W., Zielińska M., Salsac M.-D., Blanc A., Jentschel M., Köster U., Mutti P., Soldner T., Simpson G.S., Drouet F., Vancraeyenest A., de France G., Clément E., Stezowski O., Ur C.A., Urban W., Regan P.H., Podolyák Zs., Larijani C., Townsley C., Carroll R., Wilson E., Mach H., Fraile L.M., Paziy V., Olaizola B., Vedia V., Bruce A.M., Roberts O.J., Smith J.F., Scheck M., Kröll T., Hartig A.-L., Ignatov A., Ilieva S., Lalkovski S., Mărginean N., Otsuka T., Shimizu N., Togashi T., and Tsunoda Y.
Subjects: Physics, QC1-999
Abstract: Lifetimes of excited states of the 98;100;102Zr nuclei were measured by using the Generalized Centroid Difference Method. The nuclei of interest were populated via neutron-induced fission of 241Pu and 235U during the EXILL-FATIMA campaign. The obtained lifetimes were used to calculate the B(E2) transition strengths and β deformation parameters which were then compared with the recent theoretical predictions obtained with Monte Carlo Shell Model.
Published: 2018
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6. The γ-γ fast-timing technique and the EXILL&FATIMA campaign

Author: Régis J.-M., Simpson G.S., Mach H., Blanc A., Jentschel M., Köster U., Mutti P., Soldner T., de France G., Ur C.A., Urban W., Jolie J., Saed-Samii N., Warr N., Fraile L.M., Paziy V., Regan P.H., Podolyák Zs., Lalkovski S., Bruce A.M., Kröll T., Korten W., and Marginean N.
Subjects: Physics, QC1-999
Abstract: At the Institut Laue-Langevin in Grenoble, germanium-gated γ-γ fast-timing lifetime measurements of nuclear excited states in neutron-rich nuclei have been performed within a prompt γ-ray spectroscopy experimental campaign. We report on results obtained from the cold-neutron induced fission of 235U. The excited secondary fission products were stopped almost instantaneously within the thick target and the γ rays emitted were collected triggerlessly using the EXILL&FATIMA mixed array of HPGe and LaBr3(Ce) detectors. Precise lifetimes could be determined by analysing the γ-γ time difference spectra using the generalized centroid difference method. This picosecondsensitive method provides many advantages and is briefly explained. Still, the major source of systematic errors is related to the contribution of time-correlated Compton background. The EXILL&FATIMA results are discussed with respect to the typical energy-dependent timing behaviour of the background. According to the time response of the background, appropriate methods and a time correction for the sub-nanosecond regime are proposed.
Published: 2018
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7. Impact of shell evolution on Gamow-Teller β decay from a high-spin long-lived isomer in 127Ag

Author: Watanabe, H., Yuan, C.X., Lorusso, G., Nishimura, S., Xu, Z.Y., Sumikama, T., Söderström, P.-A., Doornenbal, P., Browne, F., Gey, G., Jung, H.S., Taprogge, J., Vajta, Zs., Wang, H.K., Wu, J., Yagi, A., Baba, H., Benzoni, G., Chae, K.Y., Crespi, F.C.L., Fukuda, N., Gernhäuser, R., Inabe, N., Isobe, T., Jungclaus, A., Kameda, D., Kim, G.D., Kim, Y.K., Kojouharov, I., Kondev, F.G., Kubo, T., Kurz, N., Kwon, Y.K., Lane, G.J., Li, Z., Moon, C.-B., Montaner-Pizá, A., Moschner, K., Naqvi, F., Niikura, M., Nishibata, H., Nishimura, D., Odahara, A., Orlandi, R., Patel, Z., Podolyák, Zs., Sakurai, H., Schaffner, H., Simpson, G.S., Steiger, K., Suzuki, H., Takeda, H., Wendt, A., and Yoshinaga, K.
Published: 2021
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8. Impact of shell evolution on Gamow-Teller Decay From a High-spin Long-lived Isomer in Ag

Author: Watanabe, H., Yuan, C.X., Lorusso, G., Nishimura, S., Xu, Z.Y., Sumikama, T., Söderström, P.A., Doornenbal, P., Browne, F., Gey, G., Jung, H.S., Taprogge, J., Vajta, Zs., Wang, H.K., Wu, J., Yagi, A., Baba, H., Benzoni, G., Chae, K.Y., Crespi, F.C.L., Fukuda, N., Gernhäuser, R., Inabe, N., Isobe, T., Jungclaus, A., Kameda, D., Kim, G.D., Kim, Y.K., Kojouharov, I., Kondev, F.G., Kubo, T., Kurz, N., Kwon, Y.K., Lane, G.J., Li, Z., Moon, C.B., Montaner-Pizá, A., Moschner, K., Naqvi, F., Niikura, M., Nishibata, H., Nishimura, D., Odahara, A., Orlandi, R., Patel, Z., Podolyák, Zs., Sakurai, H., Schaffner, H., Simpson, G.S., Steiger, K., Suzuki, H., Takeda, H., Wendt, A., and Yoshinaga, K.
Abstract: The change of the shell structure in atomic nuclei, so-called “nuclear shell evolution”, occurs due to changes of major configurations through particle-hole excitations inside one nucleus, as well as due to variation of the number of constituent protons or neutrons. We have investigated how the shell evolution affects Gamow-Teller (GT) transitions that dominate the β decay in the region below $^{132}$Sn using the newly obtained experimental data on a long-lived isomer in $^{127}$Ag. The T1/2=67.5(9) ms isomer has been identified with a spin and parity of (27/2+) at an excitation energy of 1942−20+14 keV, and found to decay via an internal transition of an E3 character, which competes with the dominant β-decay branches towards the high-spin states in $^{127}$Cd. The underlying mechanism of a strong GT transition from the $^{127}$Ag isomer is discussed in terms of configuration-dependent optimization of the effective single-particle energies in the framework of a shell-model approach.
Published: 2021

9. Boulay et al. Reply: Comment on 'g Factor of the Zr99(7/2+) Isomer: Monopole Evolution in the Shape-Coexisting Region'

Author: Boulay, F., Simpson, G.S., Ichikawa, Y., Kisyov, S., Bucurescu, D., Takamine, A., Ahn, D.S., Asahi, K., Baba, H., Balabanski, D.L., Egami, T., Fujita, T., Fukuda, N., Funayama, C., Furukawa, T., Georgiev, G., Gladkov, A., Hass, M., Imamura, K., Inabe, N., Ishibashi, Y., Kawaguchi, T., Kawamura, T., Kim, W., Kobayashi, Y., Kojima, S., Kusoglu, A., Lozeva, R., Momiyama, S., Mukul, I., Niikura, M., Nishibata, H., Nishizaka, T., Odahara, A., Ohtomo, Y., Ralet, D., Sato, T., Shimizu, Y., Sumikama, T., Suzuki, H., Takeda, H., Tao, L.C., Togano, Y., Tominaga, D., Ueno, H., Yamazaki, H., Yang, X.F., Daugas, J.M., Direction des Applications Militaires (DAM), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Grand Accélérateur National d'Ions Lourds (GANIL), Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3), RIKEN Nishina Center for Accelerator-Based Science [Wako] (RIKEN RNC), RIKEN - Institute of Physical and Chemical Research [Japon] (RIKEN), Laboratoire de Physique Subatomique et de Cosmologie (LPSC), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA), Centre de Sciences Nucléaires et de Sciences de la Matière (CSNSM), Université Paris-Sud - Paris 11 (UP11)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), and Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris-Sud - Paris 11 (UP11)
Subjects: 21.60.-n, 25.70.Mn, 23.20.En, [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], numbers: 21.10.Ky, ComputingMilieux_MISCELLANEOUS
Abstract: International audience
Published: 2021

10. Structure of high-lying levels populated in the 96Y →96Zr β decay

Author: Mashtakov, K.R., Ponomarev, V.Yu., Scheck, M., Finch, S.W., Isaak, J., Zweidinger, M., Agar, O., Bathia, C., Beck, T., Beller, J., Bowry, M., Chapman, R., Chishti, M.M.R., Friman-Gayer, U., Gaffney, L.P., Garrett, P.E., Gregor, E.T., Keatings, J.M., Köster, U., Löher, B., MacLean, A.D., O'Donnell, D., Pai, H., Pietralla, N., Rainovski, G., Ramdhane, M., Romig, C., Rusev, G., Savran, D., Simpson, G.S., Sinclair, J., Sonnabend, K., Spagnoletti, P., Tonchev, A.P., and Tornow, W.
Published: 2021
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11. Magnetic moment of the 11/2 − isomeric state in 99 Mo and neutron spin g factor quenching in A∼100 nuclei

Author: Daugas, J.M., Rosse, B., Balabanski, D.L., Bucurescu, D., Kisyov, S., Regan, P.H., Georgiev, G., Gaudefroy, L., Gladnishki, K., Méot, V., Morel, P., Pietri, S., Roig, O., Simpson, G.S., DAM Île-de-France (DAM/DIF), Direction des Applications Militaires (DAM), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Université Paris Saclay, Extreme Light Infrastruture - Nuclear Physics (ELI-NP), National Institut for Nuclear Physics and Engineering (IFIN HH), National Institut for Nuclear Physics and Engineering, Romanian Academy, Department of Physics, University of Surrey, University of Surrey (UNIS), National Physical Laboratory [Teddington] (NPL), Université Paris-Saclay, CNRS/IN2P3, IJCLab, 91405 Orsay, France, Faculty of Physics, Sofia University saint Kliment Ohridski, Helmholtz Centre for Heavy Ion Research (GSI), Laboratoire de Physique Subatomique et de Cosmologie (LPSC), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA), 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), and Sofia University 'St. Kliment Ohridski'
Subjects: [PHYS]Physics [physics]
Abstract: International audience; The gyromagnetic factor of the low-lying Ex=684.10(19)keV isomeric state of the nucleus 99Mo was measured using the time-dependent perturbed angular distribution technique. This level is assigned a spin and parity of Jπ=11/2−, with a half-life of T1/2=742(13)ns. The state of interest was populated and spin-aligned via a single-neutron transfer on a highly enriched 98Mo target. A magnetic moment μexpt.=−0.627(20)μN was obtained. This result is far from the Schmidt value expected for a pure single-particle νh11/2 state. A comparison of experimental spectroscopic properties of this nucleus is made with results of multishell Interacting boson-fermion Model (IBFM-1) calculations. In this approach, the Jπ=11/2− isomeric state in 99Mo has a pure νh11/2 configuration. Its magnetic moment, as well as that of other two excited states could be reasonably well reproduced by reducing the free neutron spin g factor with a quenching factor of 0.45. This low value is not appropriate only for this case, similar values for the quenching factor being also required in order to describe magnetic moments in other nuclei from the same mass region
Published: 2021

12. Structure of high-lying levels populated in the Y → Zr Decay

Author: Mashtakov, K.R., Ponomarev, V.Yu., Scheck, M., Finch, S.W., Isaak, J., Zweidinger, M., Agar, O., Bathia, C., Beck, T., Beller, J., Bowry, M., Chapman, R., Chishti, M.M.R., Friman-Gayer, U., Gaffney, L.P., Garrett, P.E., Gregor, E.T., Keatings, J.M., Köster, U., Löher, B., MacLean, A.D., O'Donnell, D., Pai, H., Pietralla, N., Rainovski, G., Ramdhane, M., Romig, C., Rusev, G., Savran, D., Simpson, G.S., Sinclair, J., Sonnabend, K., Spagnoletti, P., Tonchev, A.P., and Tornow, W.
Abstract: The nature of the high-lying final levels of the $^{96}$Y$_{gs}$ β decay, one of the three most important contributors to the high-energy reactor antineutrino spectrum, has been investigated in high-resolution γ-ray spectroscopy following the β decay as well as in a campaign of inelastic photon scattering experiments. The comprehensive approach establishes 1$^{−}$ levels associated with the Pygmy Dipole Resonance as high-lying final levels in the β decay. Branching ratios extracted from β decay complement photon scattering and allow the absolute E1 excitation strength to be determined for levels populated in both reactions. The combined data represents a comprehensive approach to the wavefunction of the 1− levels below the Qβ value, which are investigated in the Quasiparticle Phonon Model. The calculations reveal that the components populated in β decay contribute only with small amplitudes to the complex wavefunction of these 1$^{−}$ levels. A comparison of the β decay results to data from total absorption γ-ray spectroscopy demonstrates a good agreement between both measurements.
Published: 2021

13. Reinterpretation of excited states in $^{212}$Po: Shell-model multiplets rather than $\alpha$-cluster states

Author: Fernández, A., Jungclaus, A., Golubev, P., Rudolph, D., Sarmiento, L.G., Gargano, A., Naïdja, H., Astier, A., Dupont, E., Gadea, A., Nácher, E., Perea, A., Wimmer, K., Clément, E., Fremont, G., Goupil, J., Houarner, C., Jacquot, B., Korichi, A., Lemasson, A., Li, H.J., Ljungvall, J., Ménager, L., Pérez-Vidal, R.M., Petrache, C.M., Ralet, D., Ropert, J.A., Saillant, F., Såmark-Roth, A., Simpson, G.S., Spitaels, C., Zielinska, M., Ansari, S., Dudouet, J., Illana, A., Jurado, M., Kocheva, D., Lalović, N., Lorenz, Ch., Quintana, B., Rainovski, G., Redon, N., Tocabens, G., Barrientos, D., Benzoni, G., Birkenbach, B., Boston, A.J., Boston, H.C., Bracco, A., Ciemala, M., Collado, J., Cullen, D.M., Domingo-Pardo, C., Eberth, J., González, V., Harkness-Brennan, L.J., Hess, H., Judson, D.S., Korten, W., Leoni, S., Maj, A., Menegazzo, R., Mengoni, D., Michelagnoli, C., Million, B., Napoli, D.R., Nyberg, J., Podolyak, Zs., Pullia, A., Reiter, P., Sanchis, E., Stezowski, O., Theisen, Ch., Valiente-Dobón, J.J., 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), Grand Accélérateur National d'Ions Lourds (GANIL), Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3), Laboratoire de Physique Subatomique et de Cosmologie (LPSC), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA), Institut de Recherches sur les lois Fondamentales de l'Univers (IRFU), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Institut de Physique des 2 Infinis de Lyon (IP2I Lyon), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS), Institut Laue-Langevin (ILL), ILL, Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Université Claude Bernard Lyon 1 (UCBL), and Université de Lyon-Université de Lyon-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)
Subjects: [PHYS.NUCL]Physics [physics]/Nuclear Theory [nucl-th], Astrophysics::High Energy Astrophysical Phenomena, Nuclear Physics - Theory
Abstract: International audience; A $\gamma$ -ray spectroscopic study of $^{212}$Po was performed at the Grand Accélérateur National d’Ions Lourds, using the inverse kinematics α-transfer reaction $^{12}$C($^{208}$Pb, $^{212}$Po) $^8$Be and the AGATA spectrometer. A careful analysis based on $\gamma \gamma$ coincidence relations allowed us to establish 14 new excited states in the energy range between 1.9 and 3.3 MeV. None of these states, however, can be considered as candidates for the levels with spins and parities of $1^-$ and $2^-$ and excitation energies below 2.1 MeV, which have been predicted by recent αcluster model calculations. A systematic comparison of the experimentally established excitation scheme of $^{212}$Po with shell-model calculations was performed. This comparison suggests that the six states with excitation energies (spins and parities) of 1744 (4$^-$), 1751 (8$^-$), 1787 (6$^-$), 1946 (4$^-$), 1986 (8$^-$), and 2016 (6$^-$) keV, which previously were interpreted as α-cluster states, may in fact be of positive parity and belong to low-lying shell-model multiplets. This reinterpretation of the structure of $^{212}$Po is supported by experimental information with respect to the linear polarization of $\gamma$ rays, which suggests a magnetic character of the 432-keV $\gamma$ ray decaying from the state at an excitation energy of 1787 keV to the $6^+_1$ yrast state, and exclusive reaction cross sections.
Published: 2021

14. Three-quasiparticle isomers in odd-even $^{159,161}\mathrm{Pm}$: Calling for modified spin-orbit interaction for the neutron-rich region

Author: Yokoyama, R., Ideguchi, E., Simpson, G.S., Tanaka, Mn., Sun, Yang, Lv, Cui-Juan, Liu, Yan-Xin, Wang, Long-Jun, Nishimura, S., Doornenbal, P., Lorusso, G., Söderström, P.-A., Sumikama, T., Wu, J., Xu, Z.Y., Aoi, N., Baba, H., Bello Garrote, F.L., Benzoni, G., Browne, F., Daido, R., Fang, Y., Fukuda, N., Gottardo, A., Gey, G., Go, S., Inabe, S., Isobe, T., Kameda, D., Kobayashi, K., Kobayashi, M., Kojouharov, I., Komatsubara, T., Kubo, T., Kurz, N., Kuti, I., Li, Z., Matsushita, M., Michimasa, S., Moon, C.B., Nishibata, H., Nishizuka, I., Odahara, A., Patel, Z., Rice, S., Sahin, E., Sakurai, H., Schaffner, H., Sinclair, L., Suzuki, H., Takeda, H., Taprogge, J., Vajta, Zs., Watanabe, H., Yagi, A., Laboratoire de Physique Subatomique et de Cosmologie (LPSC), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA), Institut Laue-Langevin (ILL), and ILL
Subjects: [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex]
Abstract: International audience; Neutron-rich Pm (Z=61) isotopes were studied by delayed γ-ray spectroscopy at RIBF, RIKEN Nishina Center using the in-flight fission of a 345 MeV/nucleon U238 beam. A cluster-type Ge detector array, EURICA, was used to measure the delayed γ rays from stopped ions. Isomeric γ decays were observed in Pm159 and Pm161 with half-lives of 4.97(12) μs and 0.79(4) μs, respectively. Level schemes for Pm159 and Pm161 were constructed in this study. The isomeric states of Pm159 and Pm161 could be interpreted as two quasiparticle excitations of neutrons with the configurations of ν(7/2[633]⊗5/2[523]) and ν(7/2[633]⊗1/2[521]), respectively. They are analogous to the isomers that have been observed systematically in other even-mass N=98 and N=100 isotones in this region. A projected shell model calculation was performed and it reproduced the order of three-quasiparticle states only if new Nilsson parameters with an N-dependent spin-orbit interaction were used. This work demonstrates that the strength of spin-orbit interactions in standard Nilsson parameters needs to be modified to study the properties of neutron-rich rare-earth nuclei around A=165, and provides new evidence supporting the existence of the deformed N=98 subshell gap in odd-mass nuclei for the first time.
Published: 2021

15. β-decay half-lives of neutron-rich nuclei around 158Nd, relevant to the formation of the A≈165 rare-earth element peak

Author: Wu J., Nishimura S., Lorusso G., Xu Z.Y., Ideguchi E, Simpson G.S., Baba H., Browne F., Daido R., Doornebal P., Fang Y.F., Isobe T., Li Z., Patel Z., Rice S., Sinclair L., Söderström P.-A., Sumikama T., Watanabe H., Yagi A., Yokoyama R., Aoi N., Garrote F.L. Bello, Benzoni G., Gey G., Gottardo A., Nishibata H., Odahara A., Sakurai H., Tanaka M., Taprogge J., and Yamamoto T.
Subjects: Physics, QC1-999
Abstract: A β-decay spectroscopy experiment around 158Nd was performed at RI Beam Factory (RIBF), RIKEN Nishina Center, in order to understand the production mechanism of the A≈165 rare-earth element (REE) peak in the r-process mass abundance pattern. In this experiment, 53 half-lives are measured including 34 new results, which could be employed in a fully dynamic r-process network calculation.
Published: 2016
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16. Fast-timing study of Ga 81 from the β decay of Zn 81

Author: Paziy, V., Fraile, L.M., Mach, H., Olaizola, B., Simpson, G.S., Aprahamian, A., Bernards, C., Briz, José Antonio, Bucher, B., Chiara, C.J., Dlouhý, Z., Gheorghe, I., Ghita, D., Hoff, P., Jolie, J., Köster, U., Kurcewicz, W., Lică, R., Marginean, N., Marginean, R., Régis, J.M., Rudigier, M., Sava, T., Stanoiu, M., Stroe, L., Walters, W.B., Ministerio de Economía y Competitividad (España), Ministerio de Ciencia, Innovación y Universidades (España), Department of Energy (US), Federal Ministry of Education and Research (Germany), Universidad Complutense de Madrid, and European Commission
Abstract: 18 pags., 10 figs., 4 tabs., The β- decay of Zn81 to the neutron magic N=50 nucleus Ga81, with only three valence protons with respect to Ni78, was investigated. The study was performed at the ISOLDE facility at CERN by means of γ spectroscopy. The Zn81 half-life was determined to be T1/2=290(4) ms while the β-delayed neutron emission probability was measured as Pn=23(4)%. The analysis of the β-gated γ-ray singles and γ-γ coincidences from the decay of Zn81 provides 47 new levels and 70 new transitions in Ga81. The β-n decay of Zn81 was observed and a new decay scheme into the odd-odd Ga80 nucleus was established. The half-lives of the first and second excited states of Ga81 were measured via the fast-timing method using LaBr3(Ce) detectors. The level scheme and transition rates are compared to large-scale shell-model calculations. The low-lying structure of Ga81 is interpreted in terms of the coupling of the three valence protons outside the doubly magic Ni78 core., This work was supported by the Spanish MINECO through the FPA2015-65035-P and RTI2018-098868-B-I00 projects, by the U.S. DoE Grant No. DE-FG02-94ER40834, by the German BMBF Grant 05P19PKFNA, and Grupo de Física Nuclear (GFN) at UCM. The support by the European Union Seventh Framework through ENSAR (Contract No. 262010) and ISOLDE (CERN) Collaboration is acknowledged. V.P. acknowledges support by the Spanish FPI-BES-2011-045931 grant.
Published: 2020

17. Shape evolution of neutron-rich Mo 106,108,110 isotopes in the triaxial degree of freedom

Author: Ha, J., Sumikama, T., Browne, F., Hinohara, N., Bruce, A.M., Choi, S., Nishizuka, I., Nishimura, S., Doornenbal, P., Lorusso, G., Söderström, P.A., Watanabe, H., Daido, R., Patel, Z., Rice, S., Sinclair, L., Wu, J., Xu, Z.Y., Yagi, A., Baba, H., Chiga, N., Carroll, R., Didierjean, F., Fang, Y., Fukuda, N., Gey, G., Ideguchi, E., Inabe, N., Isobe, T., Kameda, D., Kojouharov, I., Kurz, N., Kubo, T., Lalkovski, S., Li, Z., Lozeva, R., Nishibata, H., Odahara, A., Podolyák, Z., Regan, P.H., Roberts, O.J., Sakurai, H., Schaffner, H., Simpson, G.S., Suzuki, H., Takeda, H., Tanaka, M., Taprogge, J., Werner, V., RIKEN Nishina Center for Accelerator-Based Science, Japan Society for the Promotion of Science, Science and Technology Facilities Council (UK), Department of Energy (US), Federal Ministry of Education and Research (Germany), Ministerio de Ciencia e Innovación (España), National Measurement Office (UK), and University of Tsukuba
Abstract: 24 pags., 17 figs., 4 tabs., Background: Neutron-rich nuclei with mass number between 100 and 110 attract much attention, since several kinds of shapes, such as spherical, prolate, oblate, and triaxial shapes, are predicted. In particular, for neutron-rich Mo isotopes, different models predict different magnitudes and rigidity of triaxial deformation. Previous interpretations of experimental results based solely on low-lying 22+ states are insufficient to distinguish between the rigid triaxial shape, γ vibration, or γ-soft rotor. Purpose: The shape evolution of Mo106, Mo108, and Mo110 is investigated through their 21+-state lifetimes, decay-branching ratios of the 22+ state, and energies of the low-lying collective excited states with Kπ=0+,2+, and 4+. Method: β-delayed γ-ray spectroscopy was employed for neutron-rich Nb and Zr isotopes produced at the RIKEN RI Beam Factory to populate excited states in Mo106, Mo108, and Mo110. The EUroball-RIKEN Cluster Array was used for high-resolution γ-ray detection and lifetimes of the 21+ states were determined using the UK fast-timing array of LaBr3(Ce) detectors. Results: New γ-ray transitions and levels are reported, including newly assigned 02+ states in Mo108,110. Quadrupole deformations were obtained for Mo106,108,110 from their 21+ energies and lifetimes. The β-delayed neutron-emission probabilities of Nb108 and Nb110 were determined by examining the γ rays of their respective daughter decays. Conclusions: The even-odd energy staggering in the 22+ band was compared with typical patterns of the γ-vibrational band, rigid triaxial rotor, and γ-soft rotor. The very small even-odd staggering of Mo106, Mo108, and Mo110 favors a γ-vibrational band assignment. The kinematic moment of inertia for the 22+ band showed a trend similar to the ground-state band, which is as expected for the γ-vibrational band. Beyond-mean-field calculations employing the constrained Hartree-Fock-Bogoliubov and local quasiparticle-random-phase approximation method using the SLy5+T interaction reproduced the ground and 22+ bands in Mo106 and Mo108. The collective wave functions are consistent with the interpretation of the 22+ band as the γ-vibrational band of the prolate shape. However, the staggering pattern observed in Mo110 differs from the one suggested in the calculations which predict a γ-soft rotor. There was no experimental indication of the oblate shape or the γ-soft rotor predicted in these Mo isotopes., We would like to express our gratitude to the RIKEN Nishina Center accelerator staff for providing a stable and high intensity 238U primary beam. This work was supported by JSPS KAKENHI Grants No. 24740188, No. 25247045, No. 26800117, and No. 16K17680; NRF Grant No. 2016K1A3A7A09005575; STFC Grants No. ST/J000132/1, No. ST/J000051/1, and No. ST/K502431/1; DOE Grant No. DE-FG02-91ER-40609; BMBF Grant No. 05P19RDFN1; and Spanish Ministerio de Ciencia e Innovación under Contracts No. FPA2009-13377-C02 and No. FPA2011- 29854-C04. P.H.R. acknowledges support from the UK National Measurement Office (NMO). P.-A.S. was financed by JSPS Grant No. 2301752 and the RIKEN Foreign Postdoctoral Researcher Program. We acknowledge the EUROBALL Owners Committee for the loan of germanium detectors and the PreSpec Collaboration for the readout electronics of the cluster detectors. N.H. acknowledges the JSPS-NSFC Bilateral Program for the Joint Research Project on “Nuclear mass and life for unravelling mysteries of r-process.” Numerical calculations were performed in part using the COMA (PACSIX) and Oakforest-PACS provided by Multidisciplinary Cooperative Research Program in Center for Computational Sciences, University of Tsukuba.
Published: 2020

18. Structure of high-lying levels populated in the $^{96}$Y $\rightarrow ^{96}$Zr $\beta$ decay

Author: Mashtakov, K.R., Ponomarev, V.Yu., Scheck, M., Finch, S.W., Isaak, J., Zweidinger, M., Agar, O., Bathia, C., Beck, T., Beller, J., Bowry, M., Chapman, R., Chishti, M.M.R., Friman-Gayer, U., Gaffney, L.P., Garrett, P.E., Gregor, E.T., Keatings, J.M., Köster, U., Löher, B., MacLean, A.D., O'Donnell, D., Pai, H., Pietralla, N., Rainovski, G., Ramdhane, M., Romig, C., Rusev, G., Savran, D., Simpson, G.S., Sinclair, J., Sonnabend, K., Spagnoletti, P., Tonchev, A.P., Tornow, W., HEP, INSPIRE, Institut Laue-Langevin (ILL), ILL, Laboratoire de Physique Subatomique et de Cosmologie (LPSC), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), and Université Grenoble Alpes (UGA)
Subjects: [PHYS.NEXP] Physics [physics]/Nuclear Experiment [nucl-ex], High Energy Physics::Experiment, [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], Nuclear Experiment
Abstract: The nature of $J^{\pi}=1^-$ levels of $^{96}$Zr below the $\beta$-decay $Q_{\beta}$ value of $^{96}$Y has been investigated in high-resolution $\gamma$-ray spectroscopy following the $\beta$ decay as well as in a campaign of inelastic photon scattering experiments. Branching ratios extracted from $\beta$ decay allow the absolute $E1$ excitation strength to be determined for levels populated in both reactions. The combined data represents a comprehensive approach to the wavefunction of $1^-$ levels below the $Q_{\beta}$ value, which are investigated in the theoretical approach of the Quasiparticle Phonon Model. This study clarifies the nuclear structure properties associated with the enhanced population of high-lying levels in the $^{96}$Y$_{gs}$ $\beta$ decay, one of the three most important contributors to the high-energy reactor antineutrino spectrum.
Published: 2020

19. Shape evolution of neutron-rich $^{106,108,110}\mathrm{Mo}$ isotopes in the triaxial degree of freedom

Author: Ha, J., Sumikama, T., Browne, F., Hinohara, N., Bruce, A.M., Choi, S., Nishizuka, I., Nishimura, S., Doornenbal, P., Lorusso, G., Söderström, P.A., Watanabe, H., Daido, R., Patel, Z., Rice, S., Sinclair, L., Wu, J., Xu, Z.Y., Yagi, A., Baba, H., Chiga, N., Carroll, R., Didierjean, F., Fang, Y., Fukuda, N., Gey, G., Ideguchi, E., Inabe, N., Isobe, T., Kameda, D., Kojouharov, I., Kurz, N., Kubo, T., Lalkovski, S., Li, Z., Lozeva, R., Nishibata, H., Odahara, A., Podolyák, Zs., Regan, P.H., Roberts, O.J., Sakurai, H., Schaffner, H., Simpson, G.S., Suzuki, H., Takeda, H., Tanaka, M., Taprogge, J., Werner, V., Wieland, O., Institut Pluridisciplinaire Hubert Curien (IPHC), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique Subatomique et de Cosmologie (LPSC), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA), Institut Laue-Langevin (ILL), ILL, Centre de Sciences Nucléaires et de Sciences de la Matière (CSNSM), and Université Paris-Sud - Paris 11 (UP11)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)
Subjects: [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], Nuclear Structure
Abstract: International audience; Background: Neutron-rich nuclei with mass number between 100 and 110 attract much attention, since several kinds of shapes, such as spherical, prolate, oblate, and triaxial shapes, are predicted. In particular, for neutron-rich Mo isotopes, different models predict different magnitudes and rigidity of triaxial deformation. Previous interpretations of experimental results based solely on low-lying 22+ states are insufficient to distinguish between the rigid triaxial shape, γ vibration, or γ-soft rotor. Purpose: The shape evolution of Mo106, Mo108, and Mo110 is investigated through their 21+-state lifetimes, decay-branching ratios of the 22+ state, and energies of the low-lying collective excited states with Kπ=0+,2+, and 4+. Method: β-delayed γ-ray spectroscopy was employed for neutron-rich Nb and Zr isotopes produced at the RIKEN RI Beam Factory to populate excited states in Mo106, Mo108, and Mo110. The EUroball-RIKEN Cluster Array was used for high-resolution γ-ray detection and lifetimes of the 21+ states were determined using the UK fast-timing array of LaBr3(Ce) detectors. Results: New γ-ray transitions and levels are reported, including newly assigned 02+ states in Mo108,110. Quadrupole deformations were obtained for Mo106,108,110 from their 21+ energies and lifetimes. The β-delayed neutron-emission probabilities of Nb108 and Nb110 were determined by examining the γ rays of their respective daughter decays. Conclusions: The even-odd energy staggering in the 22+ band was compared with typical patterns of the γ-vibrational band, rigid triaxial rotor, and γ-soft rotor. The very small even-odd staggering of Mo106, Mo108, and Mo110 favors a γ-vibrational band assignment. The kinematic moment of inertia for the 22+ band showed a trend similar to the ground-state band, which is as expected for the γ-vibrational band. Beyond-mean-field calculations employing the constrained Hartree-Fock-Bogoliubov and local quasiparticle-random-phase approximation method using the SLy5+T interaction reproduced the ground and 22+ bands in Mo106 and Mo108. The collective wave functions are consistent with the interpretation of the 22+ band as the γ-vibrational band of the prolate shape. However, the staggering pattern observed in Mo110 differs from the one suggested in the calculations which predict a γ-soft rotor. There was no experimental indication of the oblate shape or the γ-soft rotor predicted in these Mo isotopes.
Published: 2020

20. $g$ Factor of the $^{99}\mathrm{Zr}$ ($7/{2}^{+}$) Isomer: Monopole Evolution in the Shape-Coexisting Region

Author: Boulay, F., Simpson, G.S., Ichikawa, Y., Kisyov, S., Bucurescu, D., Takamine, A., Ahn, D.S., Asahi, K., Baba, H., Balabanski, D.L., Egami, T., Fujita, T., Fukuda, N., Funayama, C., Furukawa, T., Georgiev, G., Gladkov, A., Hass, M., Imamura, K., Inabe, N., Ishibashi, Y., Kawaguchi, T., Kawamura, T., Kim, W., Kobayashi, Y., Kojima, S., Kusoglu, A., Lozeva, R., Momiyama, S., Mukul, I., Niikura, M., Nishibata, H., Nishizaka, T., Odahara, A., Ohtomo, Y., Ralet, D., Sato, T., Shimizu, Y., Sumikama, T., Suzuki, H., Takeda, H., Tao, L.C., Togano, Y., Tominaga, D., Ueno, H., Yamazaki, H., Yang, X.F., Daugas, J.M., Direction des Applications Militaires (DAM), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Grand Accélérateur National d'Ions Lourds (GANIL), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique Subatomique et de Cosmologie (LPSC), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Institut Polytechnique de Grenoble - Grenoble Institute of Technology-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA), Centre de Sciences Nucléaires et de Sciences de la Matière (CSNSM), Université Paris-Sud - Paris 11 (UP11)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA), and Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)
Subjects: [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], Nuclear Physics
Abstract: International audience; The gyromagnetic factor of the low-lying E=251.96(9) keV isomeric state of the nucleus Zr99 was measured using the time-dependent perturbed angular distribution technique. This level is assigned a spin and parity of Jπ=7/2+, with a half-life of T1/2=336(5) ns. The isomer was produced and spin aligned via the abrasion-fission of a U238 primary beam at RIKEN RIBF. A magnetic moment |μ|=2.31(14)μN was deduced showing that this isomer is not single particle in nature. A comparison of the experimental values with interacting boson-fermion model IBFM-1 results shows that this state is strongly mixed with a main νd5/2 composition. Furthermore, it was found that monopole single-particle evolution changes significantly with the appearance of collective modes, likely due to type-II shell evolution.
Published: 2020

21. Lifetime measurements in the odd-A nucleus $^{177}$Hf

Author: Knafla, L., Alexa, P., Köster, U., Thiamova, G., Régis, J.M., Jolie, J., Blanc, A., Bruce, A.M., Esmaylzadeh, A., Fraile, L.M., De France, G., Häfner, G., Ilieva, S., Jentschel, M., Karayonchev, V., Korten, W., Kröll, T., Lalkovski, S., Leoni, S., Mach, H., Mărginean, N., Mutti, P., Pascovici, G., Paziy, V., Podolyák, Zs., Regan, P.H., Roberts, O.J., Saed-Samii, N., Simpson, G.S., Smith, J.F., Soldner, T., Townsley, C., Ur, C.A., Urban, W., Vancraeyenest, A., Warr, N., Institut Laue-Langevin (ILL), ILL, Laboratoire de Physique Subatomique et de Cosmologie (LPSC), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA), Grand Accélérateur National d'Ions Lourds (GANIL), Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3), 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), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay
Subjects: [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], Nuclear Structure
Abstract: International audience; Lifetimes of low- and high-spin states in the odd-A nucleus Hf177 were measured during the EXILL&FATIMA campaign using a spectrometer equipped with eight HPGe-Clover detectors and 16 fast-timing LaBr3(Ce) detectors. For the determination of lifetimes in the pico- to nanosecond regime, the well-established generalized centroid difference method was used. Lifetimes of the 9/2−, 9/2+, 11/2−, 11/2+ states were remeasured, the lifetimes of the 13/2−, 17/2−, 13/2+, 15/2+, and 17/2+ states were determined for the first time and an upper limit for the 19/2+ state has been established. From these lifetimes absolute reduced transition probabilities were extracted and compared to particle-rotor-model calculations and quasiparticle-phonon-model calculations showing the importance of including multipole-multipole interactions in the description of odd-A nuclei in the rare earth region.
Published: 2020

22. Low-$Z$ boundary of the $N=88-90$ shape phase transition: $^{148}\mathrm{Ce}$ near the critical point

Author: Koseoglou, P., Werner, V., Pietralla, N., Ilieva, S., Nikšić, T., Vretenar, D., Alexa, P., Thürauf, M., Bernards, C., Blanc, A., Bruce, A.M., Cakirli, R.B., Cooper, N., Fraile, L.M., De France, G., Jentschel, M., Jolie, J., Köster, U., Korten, W., Kröll, T., Lalkovski, S., Mach, H., Mărginean, N., Mutti, P., Patel, Z., Paziy, V., Podolyák, Zs., Regan, P.H., Régis, J.M., Roberts, O.J., Saed-Samii, N., Simpson, G.S., Soldner, T., Ur, C.A., Urban, W., Wilmsen, D., Wilson, E., Institut Laue-Langevin (ILL), ILL, Grand Accélérateur National d'Ions Lourds (GANIL), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-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, Laboratoire de Physique Subatomique et de Cosmologie (LPSC), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Institut Polytechnique de Grenoble - Grenoble Institute of Technology-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA), Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), and Université Grenoble Alpes (UGA)
Subjects: Nuclear Theory, [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], Nuclear Experiment, Nuclear Structure
Abstract: International audience; Excited states of the neutron-rich nucleus Ce148 have been populated by neutron-induced fission of a U235 target. Its electromagnetic decays were studied by means of γ-ray coincidence spectroscopy with fast-timing capabilities. Lifetimes of the 21+ and 41+ states of Ce148 were obtained and their E2 decay rates deduced. The B4/2=B(E2;41+→21+)/B(E2;21+→01+) ratio indicates that Ce148 is a transitional nucleus while the N=88/90 shape phase transition evolves into a gradual change of nuclear deformation for proton numbers Z
Published: 2020

23. Determination of beta-delayed neutron emission probability limits of rhodium isotopes by gamma-ray spectroscopy

Author: Science and Technology Facilities Council (UK), Department for Business, Energy and Industrial Strategy (UK), National Measurement System (UK), Department of Energy (US), Shearman, R., Shearman, G., Boso, A., Regan, P.H., Nishimura, S., Xu, Z.Y., Jungclaus, Andrea, Shimizu, Y., Simpson, G.S., Soderstrom, P.-A., Watanabe, H., Browne, F., Doornenbal, P., Gey, G., Jung, H.S., Meyer, B., Sumikama, T., Taprogge, J., Vajta, Zs., Wu, J., Baba, H., Benzoni, G., Chae, K.Y., Crespi, F.C.L., Fukuda, N., Gernhauser, R., Inabe, N., Isobe, T., Kajino, T., Kameda, D., Naqvi, F., Niikura, M., Nishibata, H., Odahara, A., Orlandi, R., Patel, Z., Podolyak, Zs., Sakurai, H., Schaffner, H., Schury, P., Shibagaki, S., Steiger, K., Suzuki, H., Takeda, H., Wendt, A., Yagi, A., Yoshinaga, K., Montaner-Pizá, A., Science and Technology Facilities Council (UK), Department for Business, Energy and Industrial Strategy (UK), National Measurement System (UK), Department of Energy (US), Shearman, R., Shearman, G., Boso, A., Regan, P.H., Nishimura, S., Xu, Z.Y., Jungclaus, Andrea, Shimizu, Y., Simpson, G.S., Soderstrom, P.-A., Watanabe, H., Browne, F., Doornenbal, P., Gey, G., Jung, H.S., Meyer, B., Sumikama, T., Taprogge, J., Vajta, Zs., Wu, J., Baba, H., Benzoni, G., Chae, K.Y., Crespi, F.C.L., Fukuda, N., Gernhauser, R., Inabe, N., Isobe, T., Kajino, T., Kameda, D., Naqvi, F., Niikura, M., Nishibata, H., Odahara, A., Orlandi, R., Patel, Z., Podolyak, Zs., Sakurai, H., Schaffner, H., Schury, P., Shibagaki, S., Steiger, K., Suzuki, H., Takeda, H., Wendt, A., Yagi, A., Yoshinaga, K., and Montaner-Pizá, A.
Abstract: The decay of five neutron-heavy rhodium isotopes were studied at the Radioactive Isotope Beam Factory (RIBF) Facility at the RIKEN Nishina Center after relativistic fission of 238U beam on a thick beryllium target. Previously unknown associated gamma-ray decay energies are reported for each nuclide, and through evaluating the intensity of the 2+ → 0+ E2 transition in the even-even palladium daughter nuclei, 120,122,124Pd, from the beta-tagged gamma-ray spectra an upper or lower limit of beta-delayed neutron emission is deduced for each nuclei. A general, expected trend of increasing Pn is observed in the direction of the neutron drip line.
Published: 2020

24. The Generalized Centroid Difference method for lifetime measurements via γ-γ coincidences using large fast-timing arrays

Author: Régis J.-M., Jolie J., Mach H., Simpson G.S., Blazhev A., Pascovici G., Pfeiffer M., Rudigier M., Saed-Samii N., Warr N., Blanc A., de France G., Jentschel M., Köster U., Mutti P., Soldner T., Ur C.A., Urban W., Bruce A.M., Drouet F., Fraile L.M., Ilieva S., Korten W., Kröll T., Lalkovski S., Mărginean S., Paziy V., Podolyák Zs., Regan P.H., Stezowski O., and Vancraeyenest A.
Subjects: Physics, QC1-999
Abstract: A novel method for direct electronic “fast-timing” lifetime measurements of nuclear excited states via γ-γ coincidences using an array equipped with N very fast high-resolution LaBr3(Ce) scintillator detectors is presented. The generalized centroid difference method provides two independent “start” and “stop” time spectra obtained without any correction by a superposition of the N(N – 1)/2 calibrated γ-γ time difference spectra of the N detector fast-timing system. The two fast-timing array time spectra correspond to a forward and reverse gating of a specific γ-γ cascade and the centroid difference as the time shift between the centroids of the two time spectra provides a picosecond-sensitive mirror-symmetric observable of the set-up. The energydependent mean prompt response difference between the start and stop events is calibrated and used as a single correction for lifetime determination. These combined fast-timing array mean γ-γ zero-time responses can be determined for 40 keV < Eγ < 1.4 MeV with a precision better than 10 ps using a 152Eu γ-ray source. The new method is described with examples of (n,γ) and (n,f,γ) experiments performed at the intense cold-neutron beam facility PF1B of the Institut Laue-Langevin in Grenoble, France, using 16 LaBr3(Ce) detectors within the EXILL&FATIMA campaign in 2013. The results are discussed with respect to possible systematic errors induced by background contributions.
Published: 2015
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25. New isomers in 125Pd79 and 127Pd81: Competing proton and neutron excitations in neutron-rich palladium nuclides towards the N = 82 shell closure

Author: Watanabe, H., Wang, H.K., Lorusso, G., Nishimura, S., Xu, Z.Y., Sumikama, T., Söderström, P.-A., Doornenbal, P., Browne, F., Gey, G., Jung, H.S., Taprogge, J., Vajta, Zs., Wu, J., Yagi, A., Baba, H., Benzoni, G., Chae, K.Y., Crespi, F.C.L., Fukuda, N., Gernhäuser, R., Inabe, N., Isobe, T., Jungclaus, A., Kameda, D., Kim, G.D., Kim, Y.K., Kojouharov, I., Kondev, F.G., Kubo, T., Kurz, N., Kwon, Y.K., Lane, G.J., Li, Z., Moon, C.-B., Montaner-Pizá, A., Moschner, K., Naqvi, F., Niikura, M., Nishibata, H., Nishimura, D., Odahara, A., Orlandi, R., Patel, Z., Podolyák, Zs., Sakurai, H., Schaffner, H., Simpson, G.S., Steiger, K., Sun, Y., Suzuki, H., Takeda, H., Wendt, A., and Yoshinaga, K.
Published: 2019
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26. New isomers in Pd And Pd : Competing proton and neutron excitations in neutron-rich palladium nuclides towards the = 82 Shell Closure

Author: Watanabe, H., Wang, H.K., Lorusso, G., Nishimura, S., Xu, Z.Y., Sumikama, T., Söderström, P.A., Doornenbal, P., Browne, F., Gey, G., Jung, H.S., Taprogge, J., Vajta, Zs., Wu, J., Yagi, A., Baba, H., Benzoni, G., Chae, K.Y., Crespi, F.C.L., Fukuda, N., Gernhäuser, R., Inabe, N., Isobe, T., Jungclaus, A., Kameda, D., Kim, G.D., Kim, Y.K., Kojouharov, I., Kondev, F.G., Kubo, T., Kurz, N., Kwon, Y.K., Lane, G.J., Li, Z., Moon, C.B., Montaner-Pizá, A., Moschner, K., Naqvi, F., Niikura, M., Nishibata, H., Nishimura, D., Odahara, A., Orlandi, R., Patel, Z., Podolyák, Zs., Sakurai, H., Schaffner, H., Simpson, G.S., Steiger, K., Sun, Y., Suzuki, H., Takeda, H., Wendt, A., and Yoshinaga, K.
Abstract: The neutron-rich isotopes of palladium have attracted considerable interest in terms of the evolution of the N=82 neutron shell closure and its influence on the r-process nucleosynthesis. In this Letter, we present the first spectroscopic information on the excited states in $^{125}$Pd$_{79}$ and $^{127}$Pd$_{81}$ studied using the EURICA γ-ray spectrometer, following production via in-flight fission of a high-intensity $^{238}$U beam at the RIBF facility. New isomeric states with half-lives of 144(4) ns and 39(6) μs have been assigned spins and parities of (23/2+) and (19/2+) in $^{125}$Pd and $^{127}$Pd, respectively. The observed level properties are compared to a shell-model calculation, suggesting the competition between proton excitations and neutron excitations in the proton-hole and neutron-hole systems in the vicinity of the doubly magic nucleus $^{132}$Sn.
Published: 2019

27. Proton Shell Evolution below $^{132}\mathrm{Sn}$: First Measurement of Low-Lying $\beta$-Emitting Isomers in $^{123,125}\mathrm{Ag}$

Author: Chen, Z.Q., Li, Z.H., Hua, H., Watanabe, H., Yuan, C.X., Zhang, S.Q., Lorusso, G., Nishimura, S., Baba, H., Browne, F., Benzoni, G., Chae, K.Y., Crespi, F.C.L., Doornenbal, P., Fukuda, N., Gey, G., Gernhäuser, R., Inabe, N., Isobe, T., Jiang, D.X., Jungclaus, A., Jung, H.S., Jin, Y., Kameda, D., Kim, G.D., Kim, Y.K., Kojouharov, I., Kondev, F.G., Kubo, T., Kurz, N., Kwon, Y.K., Li, X.Q., Lou, J.L., Lane, G.J., Li, C.G., Luo, D.W., Montaner-Pizá, A., Moschner, K., Niu, C.Y., Naqvi, F., Niikura, M., Nishibata, H., Odahara, A., Orlandi, R., Patel, Z., Podolyák, Zs., Sumikama, T., Söderström, P.A., Sakurai, H., Schaffner, H., Simpson, G.S., Steiger, K., Suzuki, H., Taprogge, J., Takeda, H., Vajta, Zs., Wang, H.K., Wu, J., Wendt, A., Wang, C.G., Wu, H.Y., Wang, X., Wu, C.G., Xu, C., Xu, Z.Y., Yagi, A., Ye, Y.L., Yoshinaga, K., Laboratoire de Physique Subatomique et de Cosmologie (LPSC), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Institut Polytechnique de Grenoble - Grenoble Institute of Technology-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA), Institut Laue-Langevin (ILL), ILL, Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), and Université Grenoble Alpes (UGA)
Subjects: [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], Nuclear Physics
Abstract: International audience; The β-delayed γ-ray spectroscopy of neutron-rich Ag123,125 isotopes is investigated at the Radioactive Isotope Beam Factory of RIKEN, and the long-predicted 1/2− β-emitting isomers in Ag123,125 are identified for the first time. With the new experimental results, the systematic trend of energy spacing between the lowest 9/2+ and 1/2− levels is extended in Ag isotopes up to N=78, providing a clear signal for the reduction of the Z=40 subshell gap in Ag towards N=82. Shell-model calculations with the state-of-the-art VMU plus M3Y spin-orbit interaction give a satisfactory description of the low-lying states in Ag123,125. The tensor force is found to play a crucial role in the evolution of the size of the Z=40 subshell gap. The observed inversion of the single-particle levels around Ag123 can be well interpreted in terms of the monopole shift of the π1g9/2 orbitals mainly caused by the increasing occupation of ν1h11/2 orbitals.
Published: 2019

28. Low-lying octupole isovector excitation in $^{144}$Nd

Author: Thürauf, M., Stoyanov, Ch., Scheck, M., Jentschel, M., Bernards, C., Blanc, A., Cooper, N., de France, G., Gregor, E.T., Henrich, C., Hicks, S.F., Jolie, J., Kaleja, O., Köster, U., Kröll, T., Leguillon, R., Mutti, P., O'Donnell, D., Petrache, C.M., Simpson, G.S., Smith, J.F., Soldner, T., Tezgel, M., Urban, W., Vanhoy, J., Werner, M., Werner, V., Zell, K.O., Zerrouki, T., Institut Laue-Langevin (ILL), ILL, Grand Accélérateur National d'Ions Lourds (GANIL), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Centre de Sciences Nucléaires et de Sciences de la Matière (CSNSM), Université Paris-Sud - Paris 11 (UP11)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique Subatomique et de Cosmologie (LPSC), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Institut Polytechnique de Grenoble - Grenoble Institute of Technology-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA), Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3), Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris-Sud - Paris 11 (UP11), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA), and Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])
Subjects: [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], Nuclear Structure
Abstract: International audience; The nature of low-lying 3− levels in Nd144 was investigated in the Nd143(n,γγ) cold neutron-capture reaction. The combination of the high neutron flux from the research reactor at the Institut Laue-Langevin and the high γ-ray detection efficiency of the EXILL setup allowed the recording of γγ coincidences. From the coincidence data precise branching ratios were extracted. Furthermore, the octagonal symmetry of the setup allowed angular-distribution measurements to determine multipole-mixing ratios. Additionally, in a second measurement the ultra-high resolution spectrometer GAMS6 was employed to conduct lifetime measurements using the gamma-ray induced Doppler-shift technique (GRID). The confirmed strong M1 component in the 33−→31− decay strongly supports the assignment of the 33− level at 2779keV as low-lying isovector octupole excitation. Microscopic calculations within the quasiparticle phonon model confirm an isovector component in the wave function of the 33− level, firmly establishing this fundamental mode of nuclear excitation in near-spherical nuclei.
Published: 2019

29. Decay properties of the level 3$^-_1$ in $^{96}$Mo

Author: Gregor, E.T., Arsenyev, N.N., Scheck, M., Shneidman, T.M., Thürauf, M., Bernards, C., Blanc, A., Chapman, R., Drouet, F., Dzhioev, A.A., De France, G., Jentschel, M., Jolie, J., Keatings, J.M., Kröll, Th, Köster, U., Leguillon, R., Mashtakov, K.R., Mutti, P., O'Donnell, D., Petrache, C.M., Simpson, G.S., Sinclair, J., Smith, J.F., Soldner, T., Spagnoletti, P., Sushkov, A.V., Urban, W., Vancraeyenest, A., Vanhoy, J.R., Werner, V., Zell, K.O., Zielińska, M., Institut Laue-Langevin (ILL), ILL, Laboratoire de Physique Subatomique et de Cosmologie (LPSC), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA), Grand Accélérateur National d'Ions Lourds (GANIL), Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3), Centre de Sciences Nucléaires et de Sciences de la Matière (CSNSM), Université Paris-Sud - Paris 11 (UP11)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-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, Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Institut Polytechnique de Grenoble - Grenoble Institute of Technology-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), and Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])
Subjects: High Energy Physics::Experiment, [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex]
Abstract: International audience; The first excited level of 96Mo was investigated in a high-statistics experiment using the 95Mo(n, γγ) cold neutron capture reaction. The measurements used the high cold neutron flux from the research reactor at Institut Laue-Langevin and employed the highly-efficient EXILL array to detect γ-ray coincidences. The recorded statistics allow identification of decay branches with only a small relative intensity including the E3 decay. With the knowledge of the newly measured branching ratio and the known transition probability, the lifetime of the level was determined and, subsequently, the strength of the other decay branches of the octupole phonon were calculated. The extracted electromagnetic decay strengths are compared to the systematics of the stable even–even molybdenum isotopes and values calculated in a Skyrme-force based quasiparticle random phase approximation and in a cluster approach. Additionally, the decay branch to the low-lying quadrupole isovector level was observed.
Published: 2019

30. Refractive indices of the optically nonlinear organic crystal (S)-3-methyl-5-nitro-N-(1-phenylethyl)-2-pyridinamine

Author: Lochran, S., Bailey, R.T., Cruickshank, F.R., Pugh, D., Sherwood, J.N., Simpson, G.S., Wallis, J.D., and Langley, P.J.
Subjects: Molecular crystals -- Research, Refractive index -- Research, Aminopyridines -- Research, Optical materials -- Research, Chemicals, plastics and rubber industries
Abstract: Research was conducted to examine the refractive indices of the optically nonlinear organic crystal (S)-3-methyl-5-nitro-N-(1-phenylethyl)-2-pyridinamine. The refractive indices were measured from 480 to 660 nm and fitted to four-parameter Sellmeier equations with an accuracy of +/-3 x 1/10 to the 3rd power to +/-5 x 1/10 to the 3rd power. The values of the n(sub x), n(sub y) and n(sub z) refractive indices at 532 nm were found from the Sellmeier equations to be 1.690, 1.901 and 1.725, respectively.
Published: 1998

31. Quadrupole collectivity in neutron-rich Cd isotopes

Author: Bönig S., Ilieva S., Kröll T., Scheck M., Balabanski D., Bauer C., Blazhev A., Bloch T., Deleanu D., Diriken J., Fernier P., Gernhäuser R., Hadyńska-Kęk K., Jungclaus A., Lutter R., Negret A., Nowak K., Orlandi R., Pakarinen J., Rainovski G., Rodríguez T.R., Schmid M. von, Seidlitz M., Siebeck B., Simpson G.S., Sisón A. Illana, Stegmann R., Stora T., Thirolf P.G., Thürauf M., Vermeulen M.J., Voulot D., Warr N., Wenander F., and Witte H. De
Subjects: Physics, QC1-999
Abstract: The investigation of the excitation energies of the 21+ –states in the neutron-rich Cd isotopes shows an irregular behaviour when approaching the neutron shell-closure at N = 82. The energy of the 21+–state in 128Cd is lower than the one in 126Cd. The transition strength B(E2, 0gs+ → 21+) in the even isotopes 122−128Cd was measured in Coulomb excitation experiments with the high-purity germanium detector array MINIBALL at REXISOLDE (CERN). The values for 122,124Cd coincide with beyond-mean-field calculations with a resultant prolate deformation, whereas 126,128Cd are better described by shell-model calculations.
Published: 2014
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32. Isomer and beta decay spectroscopy in the 132Sn region with EURICA

Author: Jungclaus A., Simpson G.S., Gey G., Taprogge J., Nishimura S., Doornenbal P., Lorusso G., Söderström P.-A., Sumikama T., Xu Z., Baba H., Browne F., Fukuda N., Inabe N., Isobe T., Jung H.S., Kameda D., Kim G.D., Kim Y.-K., Kojouharov I., Kubo T., Kurz N., Kwon Y.K., Li Z., Sakurai H., Schaffner H., Suzuki H., Takeda H., Vajta Z., Watanabe H., Wu J., Yagi A., Yoshinaga K., Bönig S., Daugas J.-M., Drouet F., Gernhäuser R., Ilieva S., Kröll T., Montaner-Pizá A., Moschner K., Mücher D., Nishibata H., Orlandi R., Steiger K., and Wendt A.
Subjects: Physics, QC1-999
Abstract: The first EURICA campaign with high intensity Uranium beams took place at RIKEN in November/December 2012. Within this campaign experiment NP1112-RIBF85 was performed dedicated to the study of the isomeric and beta decays of neutronrich Cd, In, Sn and Sb isotopes towards and beyond the N=82 neutron shell closure. In this contribution we present a first status report of the analysis of the extensive data set obtained in this experiment.
Published: 2014
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33. CRIS: A new method in isomeric beam production

Author: Lynch K.M., Billowes J., Bissell M.L., Budincevic I., Cocolios T.E., De Groote R.P., De Schepper S., Fedosseev V.N., Flanagan K.T., Franchoo S., Garcia Ruiz R.F., Heylen H., Marsh B.A., Mason P.J.R., Neyens G., Procter T.J., Rossel R.E., Rothe S., Simpson G.S., Smith A.J., Strashnov I., Stroke H.H., Walker P.M., Wendt K.D.A., and Wood R.T.
Subjects: Physics, QC1-999
Abstract: The Collinear Resonance Ionization Spectroscopy (CRIS) experiment at ISOLDE, CERN, uses laser radiation to stepwise excite and ionize an atomic beam for the purpose of ultra-sensitive detection of rare isotopes, and hyperfine-structure measurements. The technique also offers the ability to purify an ion beam that is heavily contaminated with radioactive isobars, including the ground state of an isotope from its isomer, allowing decay spectroscopy on nuclear isomeric states to be performed. The isomeric ion beam is selected by resonantly exciting one of its hyperfine structure levels, and subsequently ionizing it. This selectively ionized beam is deflected to a decay spectroscopy station (DSS). This consists of a rotating wheel implantation system for alpha- and beta-decay spectroscopy, and up to three germanium detectors around the implantation site for gamma-ray detection. Resonance ionization spectroscopy and the new technique of laser assisted nuclear decay spectroscopy have recently been performed at the CRIS beam line on the neutron-deficient francium isotopes. Here an overview of the two techniques will be presented, alongside a description of the CRIS beam line and DSS.
Published: 2013
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34. Prompt gamma ray-spectroscopy of N = 50 fission fragments

Author: Drouet F., Simpson G.S., Vancraeyenest A., Gey G., Kessedjian G., Malkiewicz T., Ramdhane M., Sage C., Thiamova G., Grahn T., Greenlees P.T., Hauschild K., Herzan A., Jakobsson U., Jones P., Julin R., Juutinen S., Ketelhut S., Lopez-Martens A., Nieminen P., Peura P., Rahkila P., Rinta-Antila S., Ruotsalainen P., Sandzelius M., Saren J., Scholey C., Sorri J., and Uusitalo J.
Subjects: Physics, QC1-999
Abstract: Excited states in the nuclei 83As and 84,86Se have been studied via prompt γ-ray spectroscopy. The nuclei were produced by the proton-induced fission of a 238U target, at the accelerator of the University of Jyväskylä. The JUROGAM-II array was used to detect prompt γ-rays and a triple-γ coincidence analysis performed. A comparison of the N = 50 nuclei with shell-model calculations reproduces the low-lying states in 83As and 84Se well. The inclusion of particle-hole excitations is necessary to correctly describe the states above ∼ 3.5 MeV.
Published: 2013
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35. Prompt γ-ray spectroscopy of the neutron-rich 124Cd

Author: Vancraeyenest A., Simpson G.S., Gey G., Greenlees P.T., Drouet F., Kessedjian G., Malkiewicz T., Ramdhane M., Sage C., Thiamova G., Grahn T., Hauschild K., Herzan A., Jakobsson U., Jones P., Julin R., Juutinen S., Ketelhut S., Lopez-Martens A., Nieminen P., Peura P., Rahkila P., Rinta-Antila S., Ruotsalainen P., Sandzelius M., Saren J., Scholey C., Sorri J., and Uusitalo J.
Subjects: Physics, QC1-999
Abstract: Prompt γ-ray spectroscopy of neutron-rich cadmium isotopes has been performed. The nuclei of interest have been populated via a 25-MeV, proton-induced fission of the 238U thick target and prompt γ-rays measured using the multi-detector HPGe array JUROGAM II. New high-spin decays have been observed and placed in the level scheme using triple coincidence gates. The experimental results are compared to shell-model calculations and show good agreement.
Published: 2013
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36. The birefringence of the optically nonlinear crystal 4-amino benzophenone

Author: Pan, F., Bailey, R.T., Cruickshank, F.R., Pugh, D., Sherwood, J.N., and Simpson, G.S.
Subjects: Benzophenone -- Research, Refraction, Double -- Research, Refractive index -- Research, Optical materials -- Measurement, Physics
Abstract: A more accurate method of obtaining the refractive indices of anisotropic prisms is introduced. Designed for prisms that undergo light polarization orthogonal to a dielectric prism axis, it does not require the orientation of the dielectric axes within a prism. It was developed on prisms made of 4-amino-benzophenone crystals characterized by low defect levels. The fitting of the linear refractive indices of ABP to Sellmeier equations and their verification via external angle of incidence observations is also discussed.
Published: 1996

37. Low-spin states in 80Ge populated in the β decay of the 80Ga 3- isomer

Author: Sekal, S., Fraile, L.M., Lica, R., Borge, M.J.G., Walters, W.B., Aprahamian, A., Benchouk, C., Bernards, C., Briz, J. A., Bucher, B., Chiara, C. J., Dlouhý, Z., Gheorghe, I., Ghita, D.G., Hoff, P., Jolie, J., Köster, U., Kurcewicz, W., Mach, H., Marginean, N., Marginean, R., Meliani, Z., Olaizola, B., Paziy, V., Régis, J.M., Rudigier, M., Sava, T., Simpson, G.S., Stanoiu, M., and Stroe, L.
Subjects: Astrophysics::High Energy Astrophysical Phenomena
Abstract: The structure of 80Ge has been investigated at the ISOLDE facility at CERN. A previous study reported for the first time a low-lying 0+2 intruder state at 639 keV, based on the coincidence with a previously unobserved 1764-keV γ ray, and suggested it as evidence for shape coexistence in 80Ge. We used the β decay from the 3− 22.4-keV state in 80Ga to enhance the population of low-spin states in 80Ge, including any excited 0+ level, and γγ coincidences to investigate it. We observed a 1764-keV γ ray in coincidence with strong transitions in 80Ge, thus not feeding the proposed 639-keV 0+2. No connecting transitions from previously known levels to the 639-keV and 2403-keV 2+3 states could be established either. Shell-model calculations for Ge isotopes and N=48 isotones were performed. They succeed to explain most of the experimental levels, but fail to reproduce the presence of a 0+2 state below ≈1200 keV in 80Ge. Our experimental findings and shell-model calculations are difficult to reconcile with a very low-lying 0+2 state in 80Ge.
Published: 2021

38. Linear electro-optic dispersion in (-)-2-(alpha-methylbenzylamino)-5-nitropyridine single crystals

Author: Bailey, R.T., Bourhill, G.H., Cruickshank, F.R., Pugh, D., Sherwood, J.N., Simpson, G.S., and Varma, K.B.R.
Subjects: Electrooptics -- Research, Pyridine -- Research, Crystals -- Research, Physics
Abstract: Measurements of linear electro-optic effect in 2-alpha-methylbenzyl-5-nitropyridine show that there is variation in the linear electro-optic effect with respect to the wavelength of incident light. Values of 2.1, 2.8, and 6.0 kilovolts at 488, 514.5 and 632.8 nanometers are exhibited by the methylbenzylamino compound as half voltages. The measurements also enable the variation of birefringence of the compound.
Published: 1994

39. The linear and nonlinear optical properties of the organic nonlinear material 4-nitro-4'-methylbenzylidene aniline

Author: Bailey, R.T., Bourhill, G., Cruickshank, F.R., Pugh, D., Sherwood, J.N., and Simpson, G.S.
Subjects: Optical materials -- Research, Nonlinear optics -- Research, Physics
Abstract: The linear and nonlinear optical properties of 4-nitro-4'-methylbenzylidene aniline (NMBA) organic material are studied. Large single NMBA crystals are grown by temperature lowering of a seeded supersaturated ethyl acetate solution. The crystals are then subjected to a series of experimental and theoretical analyses. Results reveal that both angle and wavelength noncritical phase matching are possible with the NMBA crystals.
Published: 1993

40. Macroscopic and microscopic description of low-energy collective states in $^{86,88}\mathrm{Se}$

Author: Thiamova, G., Grachev, Y., Abolghasem, M., Alexa, P., Reinhard, P.G., Rodríguez, T.R., Simpson, G.S., Laboratoire de Physique Subatomique et de Cosmologie (LPSC), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Institut Polytechnique de Grenoble - Grenoble Institute of Technology-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), and Université Grenoble Alpes (UGA)
Subjects: [PHYS.NUCL]Physics [physics]/Nuclear Theory [nucl-th], Nuclear Theory, Nuclear Experiment, Nuclear Structure
Abstract: International audience; Algebraic collective model (ACM) calculations for the even-even selenium isotopes Se86,88 have been performed to describe collective properties of these two transitional nuclei with only two and four valence neutrons, respectively. From the perspective of the ACM the nuclei turn out to be only weakly deformed, described by a very γ-soft potential. This is confirmed by Skyrme and Gogny energy density functional calculations. Additionally, the fully microscopic symmetry conserving configuration mixing method with the Gogny interaction has been applied to the study of these isotopes. The results show the transitional character of Se86 and the relevant role of the triaxial degree of freedom in the structure of these nuclei.
Published: 2018

41. New insights into triaxiality and shape coexistence from odd-mass $^{109}$Rh

Author: Bucher, B., Mach, H., Aprahamian, A., Robledo, L.M., Simpson, G.S., Rissanen, J., Ghiţă, D.G., Olaizola, B., Kurcewicz, W., Äystö, J., Eronen, T., Fraile, L.M., Jokinen, A., Karvonen, P., Moore, I.D., Penttilä, H., Reponen, M., Ruchowska, E., Saastamoinen, A., Smith, M.K., Weber, C., Laboratoire de Physique Subatomique et de Cosmologie (LPSC), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Institut Polytechnique de Grenoble - Grenoble Institute of Technology-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), and Université Grenoble Alpes (UGA)
Subjects: Nuclear Theory, collective levels, [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], ydinfysiikka, Nuclear Experiment, Nuclear Structure, nuclear structure and decays
Abstract: International audience; Rapid shape evolutions near A=100 are now the focus of much attention in nuclear science. Much of the recent work has been centered on isotopes with Z≤40, where the shapes are observed to transition between near-spherical to highly deformed with only a single pair of neutrons added. At higher Z, the shape transitions become more gradual as triaxiality sets in, yet the coexistence of varying shapes continues to play an important role in the low-energy nuclear structure, particularly in the odd-Z isotopes. This work aims to characterize competing shapes in the triaxial region between Zr and Sn isotopes using ultrafast timing techniques to measure lifetimes of excited states in the neutron-rich nucleus Rh109. The measurements confirm the persistence at higher Z of similarly large deformations observed near Z=40. Moreover, we show that new self-consistent mean-field calculations, with proper treatment of the odd nucleon, are able to reproduce the coexisting triaxial and highly deformed configurations revealing, for the first time, the important contribution of the unpaired nucleon to these different shapes based on the blocking of specific single-particle orbitals.
Published: 2018

42. Low-spin excitations in $^{97}$Zr

Author: Rząca-Urban, T., Urban, W., Czerwiński, M., Wiśniewski, J., Blanc, A., Faust, H., Jentschel, M., Mutti, P., Köster, U., Soldner, T., de France, G., Simpson, G.S., Ur, C.A., Institut Laue-Langevin (ILL), ILL, Grand Accélérateur National d'Ions Lourds (GANIL), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique Subatomique et de Cosmologie (LPSC), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Institut Polytechnique de Grenoble - Grenoble Institute of Technology-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA), Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA), and Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])
Subjects: [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], Nuclear Experiment, Nuclear Structure
Abstract: International audience; The main goal of this work is the determination of spins and parities of excited states in Zr97, among others the 2264.3-keV level, which had previously been tentatively reported as the 11/2− excitation corresponding to the h11/2 neutron orbital. Low-spin excited states in Zr97 were populated via the cold-neutron capture reaction. The γ rays emitted following the reaction were measured using the highly efficient array of high-purity germanium detectors, EXILL, at the Institut-Laue-Langevin (ILL), Grenoble. The primary γ rays deexciting the capture state in Zr97 were identified for the first time. The new, precise neutron binding energy in Zr97 of 5569.15(4) keV differs significantly from the value reported in the literature. The previously reported level scheme has been amended by several new low-spin levels. The (n,γ) data were complemented by a measurement of the β− decay of Y97 at the Lohengrin fission-fragment separator of the ILL, and the observation of the β− decay of Y97 populated in neutron-induced fission of U235 and measured using the EXILL Ge array. The combined data allowed unique spin-parity assignments for many levels in Zr97. The 2264.3-keV level, with a new spin-parity assignment of 9/2+, may correspond to the νg9/2 extruder orbital.
Published: 2018

43. Observation of a γ-decaying millisecond isomeric state in 128Cd80

Author: Jungclaus, A., Grawe, H., Nishimura, S., Doornenbal, P., Lorusso, G., Simpson, G.S., Söderström, P.-A., Sumikama, T., Taprogge, J., Xu, Z.Y., Baba, H., Browne, F., Fukuda, N., Gernhäuser, R., Gey, G., Inabe, N., Isobe, T., Jung, H.S., Kameda, D., Kim, G.D., Kim, Y.-K., Kojouharov, I., Kubo, T., Kurz, N., Kwon, Y.K., Li, Z., Sakurai, H., Schaffner, H., Shimizu, Y., Steiger, K., Suzuki, H., Takeda, H., Vajta, Zs., Watanabe, H., Wu, J., Yagi, A., Yoshinaga, K., Benzoni, G., Bönig, S., Chae, K.Y., Coraggio, L., Daugas, J.-M., Drouet, F., Gadea, A., Gargano, A., Ilieva, S., Itaco, N., Kondev, F.G., Kröll, T., Lane, G.J., Montaner-Pizá, A., Moschner, K., Mücher, D., Naqvi, F., Niikura, M., Nishibata, H., Odahara, A., Orlandi, R., Patel, Z., Podolyák, Zs., and Wendt, A.
Published: 2017
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44. Lifetime measurements of the first 2 + states in 104,106 Zr: Evolution of ground-state deformations

Author: Browne, F., Bruce, A.M., Sumikama, T., Nishizuka, I., Nishimura, S., Doornenbal, P., Lorusso, G., Söderström, P.-A., Watanabe, H., Daido, R., Patel, Z., Rice, S., Sinclair, L., Wu, J., Xu, Z.Y., Yagi, A., Baba, H., Chiga, N., Carroll, R., Didierjean, F., Fang, Y., Fukuda, N., Gey, G., Ideguchi, E., Inabe, N., Isobe, T., Kameda, D., Kojouharov, I., Kurz, N., Kubo, T., Lalkovski, S., Li, Z., Lozeva, R., Nishibata, H., Odahara, A., Podolyák, Zs., Regan, P.H., Roberts, O.J., Sakurai, H., Schaffner, H., Simpson, G.S., Suzuki, H., Takeda, H., Tanaka, M., Taprogge, J., Werner, V., and Wieland, O.
Subjects: Nuclear and High Energy Physics
Published: 2015
Full Text: View/download PDF

45. Publisher's Note: 94 beta-Decay Half-Lives of Neutron-Rich 55Cs to 67Ho: Experimental Feedback and Evaluation of the r-Process Rare-Earth Peak Formation [Phys. Rev. Lett. 118, 072701 (2017)]

Author: Wu, J, Nishimura, S, Lorusso, G, Möller, P, Ideguchi, E, Regan, P.H., Simpson, G.S., Söderström, PA, Walker, Philip M, Watanabe, Hiroshi, Lane, Gregory, Wu, J, Nishimura, S, Lorusso, G, Möller, P, Ideguchi, E, Regan, P.H., Simpson, G.S., Söderström, PA, Walker, Philip M, Watanabe, Hiroshi, and Lane, Gregory
Published: 2018

46. Spin-alignment in abrasion-fission reaction – g-factor measurement of isomeric states

Author: Daugas, J.M., Boulay, F., Simpson, G.S., Ichikawa, Y., Ahn, D.S., Balabanski, D.L., Egami, T., Fujita, T., Fukuda, N., Funayama, C., Furukawa, T., Georgiev, G., Gladkov, A., Hass, M., Imamura, K., Inabe, N., Ishibashi, Y., Kawaguchi, T., Kawamura, T., Kim, W., Kobayashi, Y., Kojima, S., Kusoglu, A., Momiyama, S., Mukul, I., Niikura, M., Nishibata, H., Nishizaka, T., Odahara, A., Ohtomo, Y., Ralet, D., Sato, T., Shimizu, Y., Shimoda, T., Sumikama, T., Suzuki, H., Takeda, H., Tao, L.C., Togano, Y., Tominaga, D., Ueno, H., Yamazaki, H., Yang, X.F., Direction des Applications Militaires (DAM), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Grand Accélérateur National d'Ions Lourds (GANIL), Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3), Laboratoire de Physique Subatomique et de Cosmologie (LPSC), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Centre National de la Recherche Scientifique (CNRS), Centre de Sciences Nucléaires et de Sciences de la Matière (CSNSM), and Université Paris-Sud - Paris 11 (UP11)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)
Subjects: [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex]
Abstract: International audience; The spin-alignment of fragments produced in spontaneous and neutroninducedfission reactions is found to be up to 40%. This amount of spin-alignmentallows the measurement of gyromagnetic factors of s isomeric states using the wellknown TDPAD method. This observable is a very sensitive probe of the singleparticlestructure of nuclear states and frequently allows one to determine thevalence nucleon configuration. Isomers produced by spontaneous fission are difficultto measure due to their low production rates and the ones produced by neutroninducedfission and selected in a spectrometer could not be measured because oneneeds to have fully stripped isotopes to preserve the spin-alignment in the vacuum.The measurement performed at the RIKEN Nishina Center accelerator usingthe abrasion-fission reaction of a 238U80+ beam at 345 MeV/u energy on the N=5999mZr and 98mY will be presented. The obtained results show the opportunity toperform gyromagnetic factors measurement of neutron-rich s-isomers produced bythe abrasion-fission reaction.
Published: 2017

47. The $\gamma-\gamma$ fast-timing technique and the EXILL&FATIMA campaign

Author: Régis, J.-M., Simpson, G.S., Mach, H., Blanc, A., Jentschel, M., Köster, U., Mutti, P., Soldner, T., De France, G., Ur, C.A., Urban, W., Jolie, J., Saed-Samii, N., Warr, N., Fraile, L.M., Paziy, V., Regan, P.H., Podolyák, Zs., Lalkovski, S., Bruce, A.M., Kröll, T., Korten, W., Marginean, N., Laboratoire de Physique Subatomique et de Cosmologie (LPSC), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Institut Laue-Langevin (ILL), Grand Accélérateur National d'Ions Lourds (GANIL), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-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, Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Institut Polytechnique de Grenoble - Grenoble Institute of Technology-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA), ILL, Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA), and Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)
Subjects: [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex]
Abstract: International audience; At the Institut Laue-Langevin in Grenoble, germanium-gated γ-γ fast-timing lifetime measurements of nuclear excited states in neutron-rich nuclei have been performed within a prompt γ-ray spectroscopy experimental campaign. We report on results obtained from the cold-neutron induced fission of 235U. The excited secondary fission products were stopped almost instantaneously within the thick target and the γ rays emitted were collected triggerlessly using the EXILL&FATIMA mixed array of HPGe and LaBr3(Ce) detectors. Precise lifetimes could be determined by analysing the γ-γ time difference spectra using the generalized centroid difference method. This picosecondsensitive method provides many advantages and is briefly explained. Still, the major source of systematic errors is related to the contribution of time-correlated Compton background. The EXILL&FATIMA results are discussed with respect to the typical energy-dependent timing behaviour of the background. According to the time response of the background, appropriate methods and a time correction for the sub-nanosecond regime are proposed.
Published: 2017

48. Spectroscopy of neutron-rich $^{194,96}$Y isotope produced in fission induced by cold neutrons

Author: Iskra, L.W., Fornal, B., Leoni, S., Bocchi, G., Blanc, A., Bottoni, S., Cieplicka-Oryńczak, N., Jentschel, M., Köster, U., Michelagnoli, C., Mutti, P., Soldner, T., De France, G., Simpson, G.S., Ur, C.A., Urban, W., Polish Academy of Sciences (PAN), Istituto Nazionale di Fisica Nucleare, Sezione di Milano (INFN), Istituto Nazionale di Fisica Nucleare (INFN), Institut Laue-Langevin (ILL), Grand Accélérateur National d'Ions Lourds (GANIL), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique Subatomique et de Cosmologie (LPSC), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Istituto Nazionale di Fisica Nucleare, Sezione di Padova (INFN, Sezione di Padova), Warsaw University of Technology [Warsaw], Vernay, Emmanuelle, ILL, Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3), and Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Centre National de la Recherche Scientifique (CNRS)
Subjects: [PHYS.NEXP] Physics [physics]/Nuclear Experiment [nucl-ex], [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex]
Abstract: International audience; The onset of the deformation in neutron-rich nuclei around A = 100 mass region has for many years remainedone of the most interesting subjects for nuclear spectroscopy study. For the neutron number N = 60, a sudden onsetof the deformation has been observed at the ground state, which is manifested by the presence of rotational bands(e.g. [1]). On the other hand the occurrence of shape coexistence in nuclei with N = 58 and 59, in this region (e.g.[2]), suggests that the evolution of the deformation is a more gradual process. In the yttrium isotopic chain, arotational band above the 4-, 496-keV isomer has been observed in the N = 59, 98Y nucleus, while there was noevidence of the deformed structure in the Y isotopes with neutron number less than N = 59. Our goal was toinvestigate N = 57, 96Y isotope where only a few states were known from beta decay study of 96Sr [3] as well as thelong 9.6-s (1140-keV) isomer [4]. Additionally, we decided to investigate whether deformed structures are stillpresent in the 94Y nucleus which lies 5 neutrons away from the N=60 boundary. So far, very little spectroscopicinformation has been gathered on 94Y – what regards higher spin yrast excitations established was only the presenceof the 1.35-μs, (5+) isomer at 1202 keV excitation energy [5]. This isomer could be used as a starting point for theidentification of structures on top of it.The yttrium-94 and 96 isotopes have been produced by fission of 235U and 241Pu targets induced by coldneutron from the reactor at Institut Laue-Langevin. The level scheme up to excitation energies in excess of 5 MeVhas been established based on multi-fold gamma-ray coincidence relationships measured with the EXILLspectrometer [6] which consists of up to 46 HPGe detectors. By exploiting delayed- and cross-coincidencetechniques, extensive structure has been delineated. During the analysis, over 50 new gamma transitions which feedpreviously known low-spin states as well as the long 9.6-s, 8+ isomer in 96Y isotope have been identified. Moreover,a new isomeric state at 1655-keV excitation energy has been located with half-life of 201 ns. Angular correlationanalysis allows to define spin-parity assignment for most of the identified levels, in particular (6+) for new isomer.By using the delayed-coincidence method it was possible to identify above the 201-ns state a few weak transitions,which seem to form a rotational band, in analogy to the structure above the 4- isomer in the 98Y isotope. In the caseof 94Y isotope over 11 new gamma transitions, which feed the previously known (5+) isomer, have been identified.Angular correlation analysis supported by shell-model consideration allowed to propose spin-parity assignmentsfor some of the new levels.The existence of the new isomeric state and the possible deformed band built on that isomer in the N = 57, 96Yisotope shed new light on the study of the onset of deformation in neutron-rich nuclei around N = 60. It shows thatthe deformed structures appear just after the subshell closure at N = 56 and evolve smoothly when passing throughN = 57-59 isotopes, to became a ground state structure in the 99Y isotope, i.e., at N = 60. The findings are in linewith the 94Y results where only spherical structures are present at low excitation energy.
Published: 2017

49. Abrupt shape transition at neutron number N = 60 : B ( E 2 ) values in $^{ 94 , 96 , 98}$Sr from fast $\gamma − \gamma$ timing

Author: Régis, M., Jolie, J., Saed-Samii, N., Warr, N., Pfeiffer, M., Blanc, A., Jentschel, M., Köster, U., Mutti, P., Soldner, T., Simpson, G.S., Drouet, F., Vancraeyenest, A., De France, G., Clément, E., Stezowski, O., Ur, A., Urban, W., Regan, H., Podolyák, Zs., Larijani, C., Townsley, C., Carroll, R., Wilson, E., Fraile, M., Mach, H., Paziy, V., Olaizola, B., Vedia, V., Bruce, A., Roberts, O. J., Smith, J. F., Scheck, M., Kröll, T., Hartig, A., Ignatov, A., Ilieva, S., Lalkovski, S., Korten, W., Mărginean, N., Otsuka, T., Shimizu, N., Togashi, T., Tsunoda, Y., Institut Laue-Langevin (ILL), ILL, Laboratoire de Physique Subatomique et de Cosmologie (LPSC), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Grand Accélérateur National d'Ions Lourds (GANIL), Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3), Institut de Physique Nucléaire de Lyon (IPNL), Centre National de la Recherche Scientifique (CNRS)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Université Claude Bernard Lyon 1 (UCBL), and Université de Lyon-Université de Lyon-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Nuclear Theory, [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], Nuclear Experiment
Abstract: International audience; Lifetimes of low-lying yrast states in neutron-rich 94,96,98Sr have been measured by Germanium-gated γ−γ fast timing with LaBr3(Ce) detectors using the EXILL&FATIMA spectrometer at the Institut Laue-Langevin. Sr fission products were generated using cold-neutron-induced fission of 235U and stopped almost instantaneously within the thick target. The experimental B(E2) values are compared with results of Monte Carlo shell-model calculations made without truncation on the occupation numbers of the orbits spanned by eight proton and eight neutron orbits and show good agreement. Similarly to the Zr isotopes, the abrupt shape transition in the Sr isotopes near neutron number N=60 is identified as being caused by many-proton excitations to its g9/2 orbit.
Published: 2017

50. Shape coexistence in the odd-odd nucleus $^{98}\mathrm{Y}$: The role of the ${g}_{9/2}$ neutron extruder

Author: Urban, W., Czerwiński, M., Kurpeta, J., Rząca-Urban, T., Wiśniewski, J., Materna, T., Iskra, Ł. W., Smith, A.G., Ahmad, I., Blanc, A., Faust, H., Köster, U., Jentschel, M., Mutti, P., Soldner, T., Simpson, G.S., Pinston, J.A., De France, G., Ur, C.A., Elomaa, V.V., Eronen, T., Hakala, J., Jokinen, A., Kankainen, A., Moore, I.D., Rissanen, J., Saastamoinen, A., Szerypo, J., Weber, C., Äystö, J., Institut de Recherches sur les lois Fondamentales de l'Univers (IRFU), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Institut Laue-Langevin (ILL), ILL, Laboratoire de Physique Subatomique et de Cosmologie (LPSC), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA), Grand Accélérateur National d'Ions Lourds (GANIL), Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Institut Polytechnique de Grenoble - Grenoble Institute of Technology-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), and Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])
Subjects: [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex]
Abstract: International audience; Excited states in $^{98}$Y, populated in neutron-induced fission of U$^{235}$ and in spontaneous fission of $^{248}$Cm and $^{252}$Cf, have been studied by means of $\gamma$ spectroscopy using the Lohengrin fission-fragment separator at ILL Grenoble and the EXILL, Eurogam2, and Gammasphere Ge arrays. Two new isomers have been found in $^{98}$Y: a deformed one with T$_{1/2}$=180(7) ns and a rotational band on top of it, and a spherical one with T$_{1/2}$=0.45(15)μs, analogous to the 8$^+$ isomer in $^{96}$Y, corresponding to the (νg7/2,πg$_{9/2}$)8$^+$ spherical configuration. Using the JYFLTRAP Penning trap, an accurate excitation energy of 465.7(7) keV has been determined for the 2.36-s isomer in $^{98}$Y. This result and the studies of excited levels in $^{98}$Zr, populated in β$^−$ decay of the isomer, indicate a new spin-parity, Iπ=(7)$^+$ for the isomer. The high spin and the decay properties of this isomer suggest the presence of the 9/2$^+$[404] neutron extruder orbital in its structure. This is consistent with the large deformation of the isomer, reported recently. The present work does not provide arguments to support the special role of the νg7/2-πg$_{9/2}$ interaction (the spin-orbit-partner, or SOP, mechanism).
Published: 2017

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