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Knafo, W.*; Thebault, T.*; Raymond, S.*; Manuel, P.*; Khalyavin, D. D.*; Orlandi, F.*; Ressouche, E.*; Beauvois, K.*; Lapertot, G.*; 金子 耕士; et al.
Physical Review X, 15(2), p.021075_1 - 021075_16, 2025/05
The discovery of multiple superconducting phases in UTe boosted research on correlated-electron physics. This heavy-fermion paramagnet was rapidly identified as a reference compound to study the interplay between magnetism and unconventional superconductivity with multiple degrees of freedom. The proximity to a ferromagnetic quantum phase transition was initially proposed as a driving force to triplet-pairing superconductivity. However, we find here that long-range incommensurate antiferromagnetic order is established under pressure. The propagation vector k
= (0.07, 0.33, 1) of the antiferromagnetic phase is close to a wavevector where antiferromagnetic fluctuations have previously been observed at ambient pressure. These elements support that UTe
is a nearly-antiferromagnet at ambient pressure. Our work appeals for theories modelling the evolution of the magnetic interactions and electronic properties, driving a correlated paramagnetic regime at ambient pressure to a long-range antiferromagnetic order under pressure. A deeper understanding of itinerant-f-electrons magnetism in UTe
will be a key for describing its unconventional superconducting phases.
Kumar, V.*; Chapman, R.*; Ollier, J.*; Orlandi, R.; Smith, J. F.*; Spohr, K.-M.*; Torres, D. A.*; Wady, P.*; 他10名*
Physical Review C, 110(4), p.044308_1 - 044308_18, 2024/10
被引用回数:1 パーセンタイル:0.00(Physics, Nuclear)Excited states of the molybdenum isotopes Mo were populated in two experiments which used fusion-fission and binary grazing reactions. In the first experiment, the GASP array of Ge detectors was used to detect
rays from fusion-fission products from the
S +
Yb reaction at 230 MeV. In the multinucleon transfer experiment, a 530-MeV beam of
Zr ions was incident on a thin
Sn target; projectile-like ejectiles were detected and identified using the PRISMA magnetic spectrometer and their associated
rays detected using the CLARA array of Clover detectors. Previously known bands were extended in all isotopes, and a new g
band was established in
Mo. The observed level schemes were compared with shell-model calculations, which reproduce the general features of the energy spectrum of excited states of
Mo,
Mo, and
Mo, although not in detail. For the h
negative-parity decay sequences of the three isotopes studied, evidence is presented for nuclear shape changes with increasing neutron number.
Benito, J.*; Lenzi, S. M.*; Recchia, F.*; Axiotis, M.*; Aydin, S.*; Bazzacco, D.*; Benzoni, G.*; Orlandi, R.; 他37名*
Acta Physica Polonica B; Proceedings Supplement, 17(3), p.3-A4_1 - 3-A4_7, 2024/04
被引用回数:0 パーセンタイル:0.00(Physics, Multidisciplinary)Excited states of neutron-rich Fe isotopes have been studied through a multinucleon transfer reaction of a
Zn beam on a
U target at the National Laboratories of Legnaro, Italy. The magnetic spectrometer PRISMA was used to identified the isotopes produced in the reaction, and the CLARA array of Clover Ge detectors to detect their gamma rays. The obtained level scheme were compared with new, state-of-the-art large scale shell model calculations. The large model space used in the calculation, which included the 2d
orbital, revealed that this orbit is key in order to obtain excellent agreement between the calculations and the experimental data.
Kumar, V.*; Chapman, R.*; O'Donnell, D.*; Ollier, J.*; Orlandi, R.; Smith, J. F.*; Spohr, K.-M.*; Torres, D. A.*; 他13名*
Physical Review C, 108(4), p.044313_1 - 044313_19, 2023/10
被引用回数:1 パーセンタイル:26.66(Physics, Nuclear)The nuclear structure of neutron-rich niobium isotopes Nb were studied at the Legnaro National Laboratories using
-ray spectroscopy. The isotopes were produced in two different experiments, either using multi-nucleon transfer reactions of
Zr 530-MeV beam onto a
Sn target, or via fusion-fission of
S on
Yb. The level schemes of these isotopes were extended respectively up to excitation energies of 4545, 5409, and 3814 keV. The structure of the low-lying states in these isotopes was interpreted and discussed in the context of shell-model calculations. In particular, for the
Nb isotope (
=41,
=58), the results indicate the presence of shape-coexistence at low-energies, which was observed for the first time in this isotope.
Pedersen, L. G.*; Sahin, E.*; Grgen, A.*; Bello Garrote, F. L.*; Orlandi, R.; 他61名*
Acta Physica Polonica B; Proceedings Supplement, 16(4), p.4-A14_1 - 4-A14_6, 2023/08
被引用回数:0 パーセンタイル:0.00(Physics, Multidisciplinary)Excited states in Cu were observed for the first time following the
decay of
Ni created by in-flight fission of
U. Based on the coincidences with the observed
-ray transitions, a level scheme comprising eight excited states was constructed, with tentative spin assignments for 5 of them. In addition to the
-decaying states, an isomeric state with a lifetime of 3.8(4) ms was also found to decay by internal conversion.
Pedersen, L. G.*; Sahin, E.*; Grgen, A.*; Bello Garrote, F. L.*; 角田 佑介*; 大塚 孝治*; 新倉 潤*; Orlandi, R.; 他59名*
Physical Review C, 107(4), p.044301_1 - 044301_10, 2023/04
被引用回数:3 パーセンタイル:45.98(Physics, Nuclear)Nuclei in the vicinity of Ni (
=28,
=50) are important benchmarks to study the evolution of shell structure far from stability. Excited states in
Cu were observed for the first time following the
-decay of
Ni, which was produced by in-flight fission of
U. Using
-ray coincidences, a level scheme comprising eight excited states was built. Using the observed
feeding and the
-decay properties of the excited states, spin was tentatively assigned to 5 new states. In addition to the
-decaying states, an isomeric state with a lifetime of 3.8(4) ms was found to decay by internal conversion. By comparing the results with large scale shell model calculations, quantitative information about the proton-neutron interaction outside the doubly magic
Ni core was obtained.
Yan, S. Q.*; Li, X. Y.*; 西尾 勝久; Lugaro, M.*; Li, Z. H.*; 牧井 宏之; Pignatari, M.*; Wang, Y. B.*; Orlandi, R.; 廣瀬 健太郎; et al.
Astrophysical Journal, 919(2), p.84_1 - 84_7, 2021/10
被引用回数:6 パーセンタイル:33.92(Astronomy & Astrophysics)The long-lived Fe (with a half-life of 2.62 Myr) is a crucial diagnostic of active nucleosynthesis in the Milky Way galaxy and in supernovae near the solar system. The neutron-capture reaction
Fe(n,
)
Fe on
Fe (half-life=44.5 days) is the key reaction for the production of
Fe in massive stars. This reaction cross section has been previously constrained by the Coulomb dissociation experiment, which offered partial constraint on the E1
-ray strength function but a negligible constraint on the M1 and E2 components. In this work, for the first time, we use the surrogate ratio method to experimentally determine the
Fe(n,
)
Fe cross sections in which all the components are included. We derived a Maxwellian-averaged cross section of 27.5
3.5 mb at
= 30 keV and 13.4
1.7 mb at
= 90 keV, roughly 10%-20% higher than previous estimates. We analyzed the impact of our new reaction rates in nucleosynthesis models of massive stars and found that uncertainties in the production of
Fe from the
Fe(n,
)
Fe rate are at most 25
. We conclude that stellar physics uncertainties now play a major role in the accurate evaluation of the stellar production of
Fe.
Bello Garrote, F. L.*; Sahin, E.*; 角田 佑介*; 大塚 孝治*; Grgen, A.*; Orlandi, R.; 他61名*
Physical Review C, 102(3), p.034314_1 - 034314_13, 2020/09
被引用回数:4 パーセンタイル:37.19(Physics, Nuclear)Detailed spectroscopy of neutron-rich odd- Cu isotopes is of great importance for studying the shell evolution in the region of
Ni. Excited states in
Cu were populated in the
decay of
Ni isotopes, which were produced by the in-flight fission at RIBF, RIKEN. The
Ni isotopes were separated, identified, and implanted in a highly segmented Si detector array for the detection of the
-decay electrons, while the delayed
rays were detected by an array of HPGe cluster detectors. A level scheme of
Cu was built up to
4 MeV, from which the location of the two previously known low-lying isomeric states was clarified. The level structure below 2 MeV was interpreted based on the results of the shell-model calculations and the systematics of odd-
Cu isotopes, revealing the evolution of single-particle states in this region.
寺田 典樹*; Qureshi, N.*; Stunault, A.*; Enderle, M.*; Ouladdiaf, B.*; Colin, C. V.*; Khalyavin, D. D.*; Manuel, P.*; Orlandi, F.*; 宮原 慎*; et al.
Physical Review B, 102(8), p.085131_1 - 085131_7, 2020/08
被引用回数:3 パーセンタイル:15.07(Materials Science, Multidisciplinary)We have determined the magnetic structures in high pressure phase with the giant ferroelectric polarization in DyMnO. For Mn spins, the E-type magnetic ordering is stabilized above 4.0 GPa, which induces the giant ferroelectric polarization through the exchange striction effect. Furthermore, we have elucidate that the lattice distortion generated through the exchange striction for the Dy and Mn bonds can give the significant magnetic field enhancement of ferroelectric polarization in this system.
Dupont, E.*; Astier, A.*; Petrache, C. M.*; Lv, B. F.*; Deloncle, I.*; Kiener, J.*; Orlandi, R.; 牧井 宏之; 西尾 勝久; 廣瀬 健太郎; et al.
Physical Review C, 101(1), p.014309_1 - 014309_6, 2020/01
被引用回数:2 パーセンタイル:20.59(Physics, Nuclear)Five new 2 levels and one new 3
level were established in
Po. The states were populated via the
Pb(
C,
Be) two-proton reaction experiment, performed at the JAEA Tandem in Tokai. A setup combining Ge, LaBr
, and Si telescopes was used to detect in-beam
-rays and ejectile residues. Two-proton configurations were assigned to all new states. All assignments are strongly supported by shell-model calculations.
牧井 宏之; 西尾 勝久; 廣瀬 健太郎; Orlandi, R.; Lguillon, R.; 小川 達彦; Soldner, T.*; K
ster, U.*; Pollitt, A.*; Hambsch, F.-J.*; et al.
Physical Review C, 100(4), p.044610_1 - 044610_7, 2019/10
被引用回数:15 パーセンタイル:77.80(Physics, Nuclear)The prompt fission -ray energy spectrum for cold-neutron induced fission of
U was measured in the energy range
= 0.8 - 20,MeV, by gaining a factor of about 10
in statistics compared to the measurements performed so far. The spectrum exhibits local bump structures at
4,MeV and
6,MeV, and also a broad one at
15,MeV. In order to understand the origins of these bumps, the
-ray spectra were calculated using a statistical Hauser-Feshbach model, taking into account the de-excitation of all the possible primary fission fragments. It is shown that the bump at
4,MeV is created by the transitions between the discrete levels in the fragments around
Sn, and the bump at
6,MeV mostly comes from the complementary light fragments. It is also indicated that a limited number of nuclides, which have high-spin states at low excitation energies, can contribute to the bump structure around
15,MeV, induced by the transition feeding into the low-lying high-spin states.
Wrzosek-Lipska, K.*; Rezynkina, K.*; Bree, N.*; Zieliska, M.*; Gaffney, L. P.*; Petts, A.*; Andreyev, A. N.; Bastin, B.*; Bender, M.*; Blazhev, A.*; et al.
European Physical Journal A, 55(8), p.130_1 - 130_23, 2019/08
被引用回数:17 パーセンタイル:79.37(Physics, Nuclear)The neutron-deficient mercury isotopes serve as a classical example of shape coexistence, whereby at low energy near-degenerate nuclear states characterized by different shapes appear. The electromagnetic structure of even-mass Hg isotopes was studied using safe-energy Coulomb excitation of neutron-deficient mercury beams delivered by the REX-ISOLDE facility at CERN. The population of 0
, 2
, and 4
states was observed in all nuclei under study. Reduced
matrix elements coupling populated yrast and non-yrast states were extracted, including their relative signs. These are a sensitive probe of shape coexistence and may be used to validate nuclear models. The experimental results are discussed in terms of mixing of two different configurations and are compared with three different model calculations: the Beyond Mean Field model, the Interacting Boson Model with configuration mixing and the General Bohr Hamiltonian. Partial agreement with experiment was observed, hinting to missing ingredients in the theoretical descriptions.
牧井 宏之; 西尾 勝久; 廣瀬 健太郎; Orlandi, R.; Lguillon, R.*; 小川 達彦; Soldner, T.*; Hambsch, F.-J.*; A
che, M.*; Astier, A.*; et al.
Nuclear Instruments and Methods in Physics Research A, 906, p.88 - 96, 2018/10
被引用回数:3 パーセンタイル:25.74(Instruments & Instrumentation)中性子誘起核分裂における即発高エネルギー線を観測するための新しい測定システムの開発を行った。測定システムは核分裂片を観測するための多芯線比例計数管と
線測定用のLaBr
(Ce)シンチレータから構成される。開発したシステムを仏国ラウエ・ランジュバン研究所にある高中性子束炉のPF1Bコースに設置して、
U中性子誘起核分裂における即発
線を行った。測定ではエネルギー最大20MeVまでの
線スペクトルの観測に成功し、
U中性子誘起核分裂において非常に高いエネルギーの
線が放出されていることを確認した。
Orlandi, R.; Pain, S. D.*; Ahn, S.*; Jungclaus, A.*; Schmitt, K. T.*; Bardayan, D. W.*; Catford, W. N.*; Chapman, R.*; Chipps, K. A.*; Cizewski, J. A.*; et al.
Physics Letters B, 785, p.615 - 620, 2018/10
被引用回数:9 パーセンタイル:56.46(Astronomy & Astrophysics)Low-lying neutron-hole states in Sn were populated via the
Sn(d,t) reaction at Oak Ridge National Laboratory. The triton angular distributions were compared to DWBA calculations and revealed spectroscopic factors compatible with a single-hole nature of the states populated. The data permit to determine the spin-orbit splitting of the strongly bound
and
neutron orbits below the shell gap, which was compared to the splitting of the weakly bound 3
and 2
orbits above the gap. The comparison revealed a smaller energy splitting of the 3
orbits. All splittings were reproduced using Woods-Saxon calculations, and the lower splitting of the 3
orbits was explained to arise from the large radial extent of the wavefunction and small value of the amplitude at the surface. This result is important to understand at a fundamental level the spin-orbit interaction, and its effects on neutron-rich nuclei.
Jentschel, M.*; Blanc, A.*; de France, G.*; Kster, U.*; Leoni, S.*; Mutti, P.*; Simpson, G.*; Soldner, T.*; Ur, C.*; Urban, W.*; et al.
Journal of Instrumentation (Internet), 12(11), p.P11003_1 - P11003_33, 2017/11
被引用回数:43 パーセンタイル:85.20(Instruments & Instrumentation)A highly efficient array of high-purity germanium (HPGe) detectors was developed and operated at the cold neutron beam facility PF1B of the Institut Laue-Langevin (ILL) to carry out nuclear structure studies, via measurements of -rays following neutron-induced capture and fission reactions. The setup consisted of a collimation system producing a pencil beam with a thermal capture equivalent flux of about 10
ns
cm
at the target position and negligible neutron halo. The target was surrounded by an array of eight to ten anti-Compton shielded EXOGAM Clover detectors, four to six anti-Compton shielded large coaxial GASP detectors and two standard Clover detectors. For a part of the campaign the array was combined with 16 LaBr
:(Ce) detectors from the FATIMA collaboration.
Wilson, G. L.*; 武山 美麗*; Andreyev, A. N.; Andel, B.*; Antalic, S.*; Catford, W. N.*; Ghys, L.*; 羽場 宏光*; Heberger, F. P.*; Huang, M.*; et al.
Physical Review C, 96(4), p.044315_1 - 044315_7, 2017/10
被引用回数:9 パーセンタイル:55.59(Physics, Nuclear)The exotic decay process of -delayed fission has been studied in the neutron-deficient isotope
Am at RIKEN, Japan. The
Am nuclei were produced in the complete fusion reaction
Pb(
Al,4n)
Am and separated by using the GARIS gas-filled recoil ion separator. A lower limit for the
-delayed fission probability larger than 0.30 was deduced, which so far is the highest value among all known nuclei exhibiting this decay mode.
Shand, C. M.*; Podolyk, Zs.*; G
rska, M.*; Doornenbal, P.*; Obertelli, A.*; Nowacki, F.*; Otsuka, T.*; Sieja, K.*; Tostevin, J. A.*; Tsunoda, T.*; et al.
Physics Letters B, 773, p.492 - 497, 2017/10
被引用回数:28 パーセンタイル:87.72(Astronomy & Astrophysics)Low-lying states in neutron-rich Zn nuclei were measured for the first time via in-beam
-ray spectroscopy at RIKEN. These include the 4
to 2
in
Zn and the 2
to 0
and 4
to 2
in
Zn. The reduced E(
) energies and increased E(4
)/E(2
) ratios at
=52,54 compared to
Zn attest that the magicity is confined just on the neutron number
=50 only. The levels observed in
Zn suggest the onset of deformation towards heavier Zn isotopes. The data were compared to state-of-the-art shell model calculations.
牧井 宏之; 西尾 勝久; 廣瀬 健太郎; Orlandi, R.; Lguillon, R.; 小川 達彦; Soldner, T.*; Hambsch, F.-J.*; Astier, A.*; Pollitt, A.*; et al.
EPJ Web of Conferences, 146, p.04036_1 - 04036_4, 2017/09
被引用回数:4 パーセンタイル:88.69(Nuclear Science & Technology)核分裂に伴い放出される即発線スペクトルの測定は高励起状態にある中性子過剰な核分裂片の脱励起過程を理解する上で重要であると同時に、革新的原子炉の設計といった応用分野においても重要である。これまで
Cfの自発核分裂においては、核分裂片の巨大共鳴振動が励起されていることを示唆する、8MeVから20MeVにおいて膨らみを持つ高エネルギー
線が観測されていることが知られている。巨大共鳴振動励起の起源を理解するためには
Cfの自発核分裂以外で即発
線スペクトルを測定する必要があるが、中性子誘起核分裂においては最近の測定においても9MeV程度までしか観測されていない。我々は
U(n,f)においても20MeVまでの即発
線スペクトルの観測を目的とした測定を仏国ラウエ・ランジュバン研究所にある高中性子束炉の大強度冷中性子ビームを用いて行った。発表では測定で得られた結果について報告する。
Jungclaus, A.*; Grawe, H.*; 西村 俊二*; Doornenbal, P.*; Lorusso, G.*; Simpson, G. S.*; Sderstr
m, P.-A.*; 炭竃 聡之*; Taprogge, J.*; Xu, Z. Y.*; et al.
Physics Letters B, 772, p.483 - 488, 2017/09
被引用回数:8 パーセンタイル:52.04(Astronomy & Astrophysics)A new high-spin isomer in the neutron-rich nucleus Cd was populated in the projectile fission of a
U beam at the Radioactive Isotope Beam Factory at RIKEN. A half-life of T
= 6.3(8) ms was measured for the new state which was tentatively assigned a spin/parity of (15
). The isomeric state decays via the emission of a 309-keV
ray with
multipolarity. The experimental results are compared to shell model calculations performed using state-of-the-art realistic effective interactions and to the neighbouring nucleus
Cd. The comparison with calculations shows that adjustments of the pairing and multipole parts of the effective interaction derived from the CD-Bonn nucleon-nucleon potential are required in order to describe the properties of nuclei in the region around
Sn.
Flavigny, F.*; Doornenbal, P.*; Obertelli, A.*; Delaroche, J.-P.*; Girod, M.*; Libert, J.*; Rodriguez, T. R.*; Authelet, G.*; 馬場 秀忠*; Calvet, D.*; et al.
Physical Review Letters, 118(24), p.242501_1 - 242501_6, 2017/06
被引用回数:40 パーセンタイル:86.20(Physics, Multidisciplinary)The first -ray spectroscopy of very neutron rich
Kr isotopes was carried out at the RIBF at RIKEN Nishina center. Excited states in these isotopes were populated via (p,2p) reactions using radioactive
Rb beams accelerated to 220 MeV/nucleon. The new data show a significant increase in deformation beyond N=60, as well as competing configurations (shape-coexistence) at low energy. The data were compared with beyond-mean-field calculations which predict level energies in good agreement with observation, and suggest oblate-prolate shape coexistence.