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論文

Fusion reaction $$^{48}$$Ca+$$^{249}$$Bk leading to formation of the element Ts (Z=117)

Khuyagbaatar, J.*; Yakushev, A.*; D$"u$llmann, Ch. E.*; Ackermann, D.*; Andersson, L.-L.*; 浅井 雅人; Block, M.*; Boll, R. A.*; Brand, H.*; Cox, D. M.*; et al.

Physical Review C, 99(5), p.054306_1 - 054306_16, 2019/05

https://doi.org/10.1103/PhysRevC.99.054306

$$^{48}$$Ca+$$^{249}$$B融合反応を用いて117番元素(Ts)合成実験を行い、117番元素に起因すると思われる4つの$$alpha$$崩壊連鎖を観測した。うち2つは長い崩壊連鎖で、$$^{294}$$Tsの$$alpha$$崩壊に起因するものと同定された。他の2つは短い崩壊連鎖で、$$^{293}$$Tsの$$alpha$$崩壊に起因すると考えると矛盾しない。今回の結果と過去の文献値を比較したところ、今回の我々の結果は過去の文献値をほぼ再現し、117番元素合成の事実を強く再確認する結果となった。

論文

Coexistence of ferromagnetic and stripe-type antiferromagnetic spin fluctuations in YFe$$_{2}$$Ge$$_{2}$$

Wo, H.*; Wang, Q.*; Shen, Y.*; Zhang, X.*; Hao, Y.*; Feng, Y.*; Shen, S.*; He, Z.*; Pan, B.*; Wang, W.*; et al.

Physical Review Letters, 122(21), p.217003_1 - 217003_5, 2019/05

https://doi.org/10.1103/PhysRevLett.122.217003

We report neutron scattering measurements of single-crystalline YFe$$_{2}$$Ge$$_{2}$$ in the normal state, which has the same crystal structure as the 122 family of iron pnictide superconductors. YFe$$_{2}$$Ge$$_{2}$$ does not exhibit long-range magnetic order but exhibits strong spin fluctuations. Like the iron pnictides, YFe$$_{2}$$Ge$$_{2}$$ displays anisotropic stripe-type antiferromagnetic spin fluctuations at ($$pi, 0, pi$$). More interesting, however, is the observation of strong spin fluctuations at the in-plane ferromagnetic wave vector ($$0, 0, pi$$). These ferromagnetic spin fluctuations are isotropic in the ($$H, K$$) plane, whose intensity exceeds that of stripe spin fluctuations. Both the ferromagnetic and stripe spin fluctuations remain gapless down to the lowest measured energies. Our results naturally explain the absence of magnetic order in YFe$$_{2}$$Ge$$_{2}$$ and also imply that the ferromagnetic correlations may be a key ingredient for iron-based materials.

論文

First ionization potentials of Fm, Md, No, and Lr; Verification of filling-up of 5f electrons and confirmation of the actinide series

佐藤 哲也; 浅井 雅人; Borschevsky, A.*; Beerwerth, R.*; 金谷 佑亮*; 牧井 宏之; 水飼 秋菜*; 永目 諭一郎; 長 明彦; 豊嶋 厚史; et al.

Journal of the American Chemical Society, 140(44), p.14609 - 14613, 2018/11

https://doi.org/10.1021/jacs.8b09068
 被引用回数：4 パーセンタイル：21.13(Chemistry, Multidisciplinary)

第一イオン化エネルギー(IP$$_1$$)は、原子の価電子軌道に関する情報を与える。99番元素アインスタイニウムよりも重いアクチノイドのIP$$_1$$は、一度に一つの原子しか扱うことのできない実験の難しさから、これまでに実験的に測定された例はなかった。我々は表面電離法を応用した新しい測定手法により、103番元素ローレンシウム(Lr)のIP$$_1$$測定に成功し、Lrが弱く束縛された最外殻電子をもつことを強く示唆する結果を得た。一方、Lrとは対象的に、102番元素ノーベリウムは充填された5f軌道および7s軌道をもつために、アクチノイド中最高のIP$$_1$$をもつと考えられている。表面電離法によるIP$$_1$$決定法をNoおよび100番元素フェルミウム, 101番元素メンデレビウムに適用することにより求められた各IP$$_1$$から、5f軌道への電子の充填に伴ってIP$$_1$$が単調に増加し、Noで最も大きくなることを確かめることができた。このことから、f軌道に電子が充填され、アクチノイド系列がLrで終わることを実験的に確かめた。

論文

A New detector system for the measurement of high-energy prompt $$gamma$$-rays for low-energy neutron induced fission

牧井 宏之; 西尾 勝久; 廣瀬 健太郎; Orlandi, R.; L$'e$guillon, R.*; 小川 達彦; Soldner, T.*; Hambsch, F.-J.*; A$"i$che, M.*; Astier, A.*; et al.

Nuclear Instruments and Methods in Physics Research A, 906, p.88 - 96, 2018/10

https://doi.org/10.1016/j.nima.2018.07.055
 パーセンタイル：100(Instruments & Instrumentation)

中性子誘起核分裂における即発高エネルギー$$gamma$$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$$gamma$$線測定用のLaBr$$_{3}$$(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、$$^{235}$$U中性子誘起核分裂における即発$$gamma$$線を行った。測定ではエネルギー最大20MeVまでの$$gamma$$線スペクトルの観測に成功し、$$^{235}$$U中性子誘起核分裂において非常に高いエネルギーの$$gamma$$線が放出されていることを確認した。

論文

Evidence of a structural quantum critical point in (Ca$$_x$$Sr$$_{1-x}$$)$$_3$$Rh$$_4$$Sn$$_{13}$$ from a lattice dynamics study

Cheung, Y. W.*; Hu, Y. J.*; 今井 正樹*; 谷奥 泰明*; 金川 響*; 村川 譲一*; 森山 広大*; Zhang, W.*; Lai, K. T.*; 吉村 一良*; et al.

Physical Review B, 98(16), p.161103_1 - 161103_5, 2018/10

https://doi.org/10.1103/PhysRevB.98.161103
 パーセンタイル：100(Materials Science, Multidisciplinary)

Approaching a quantum critical point has been an effective route to stabilize superconductivity. While the role of magnetic QCPs has been extensively discussed, similar exploration of a structural QCP is scarce. Using inelastic X-ray scattering, we examine the phonon spectrum of the nonmagnetic quasi-skutterudite (Ca$$_x$$Sr$$_{1-x}$$)$$_3$$Rh$$_4$$Sn$$_{13}$$, which represents a precious system to explore the interplay between structural instabilities and superconductivity by tuning the Ca concentration x. We unambiguously detect the softening of phonon modes around the M point on cooling towards the structural transition. Intriguingly, at x = 0:85, the soft mode energy squared at the M point extrapolates to zero at -5.7 K, providing the first compelling microscopic evidence of a structural QCP in (Ca$$_x$$Sr$$_{1-x}$$)$$_3$$Rh$$_4$$Sn$$_{13}$$. The enhanced phonon density-of-states at low energy provides the essential ingredient for realizing strong-coupling superconductivity near the structural QCP.

論文

Liquid-like thermal conduction in intercalated layered crystalline solids

Li, B.; Wang, H.*; 川北 至信; Zhang, Q.*; Feygenson, M.*; Yu, H. L.*; Wu, D.*; 尾原 幸治*; 菊地 龍弥*; 柴田 薫; et al.

Nature Materials, 17(3), p.226 - 230, 2018/03

https://doi.org/10.1038/s41563-017-0004-2
 被引用回数：18 パーセンタイル：1.81(Chemistry, Physical)

As a generic property, all substances transfer heat through microscopic collisions of constituent particles. A solid conducts heat through both transverse and longitudinal acoustic phonons, but a liquid employs only longitudinal vibrations. As a result, a solid is usually thermally more conductive than a liquid. In canonical viewpoints, such a difference also serves as the dynamic signature distinguishing a solid from a liquid. Here, we report liquid-like thermal conduction observed in the crystalline AgCrSe$$_{2}$$. The transverse acoustic phonons are completely suppressed by the ultrafast dynamic disorder while the longitudinal acoustic phonons are strongly scattered but survive, and are thus responsible for the intrinsically ultralow thermal conductivity. This scenario is applicable to a wide variety of layered compounds with heavy intercalants in the van der Waals gaps, manifesting a broad implication on suppressing thermal conduction. These microscopic insights might reshape the fundamental understanding on thermal transport properties of matter and open up a general opportunity to optimize performances of thermoelectrics.

論文

Study of fission using multi-nucleon transfer reactions

西尾 勝久; 廣瀬 健太郎; Vermeulen, M. J.; 牧井 宏之; Orlandi, R.; 塚田 和明; 浅井 雅人; 豊嶋 厚史; 佐藤 哲也; 永目 諭一郎; et al.

EPJ Web of Conferences (Internet), 163, p.00041_1 - 00041_6, 2017/11

https://doi.org/10.1051/epjconf/201716300041
 パーセンタイル：100

We are promoting a study of fission using multi-nucleon transfer (MNT) reactions, where excited states in neutron-rich actinide nuclei, which cannot be accessed by particle capture and/or fusion reactions, are populated. Also, the excited states in the fissioning nucleus are widely populated by the MNT reactions, from which effects of excitation energy on fission properties can be investigated. Experiments were carried out at the JAEA tandem facility in Tokai, Japan. We studied reactions using the $$^{18}$$O beam and several actinide target nuclei such as $$^{232}$$Th, $$^{238}$$U, $$^{237}$$Np, $$^{248}$$Cm. Ejectile nucleus was identified by a silicon $$Delta$$E-E telescope to identify transfer channel and hence the compound nucleus. Fission fragments were detected by multi-wire proportional counters, and fission fragment mass distributions (FFMDs) were measured for each isotope. Measured FFMDs are reproduced by a calculation based on the fluctuation-dissipation model, and importance of multi-chance fission concept is investigated. Fission fragment angular distribution relative to the recoil direction suggested the increase of the spin of the fissioning nucleus with the number of transferred nucleons.

論文

EXILL; A High-efficiency, high-resolution setup for $$gamma$$-spectroscopy at an intense cold neutron beam facility

Jentschel, M.*; Blanc, A.*; de France, G.*; K$"o$ster, 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

https://doi.org/10.1088/1748-0221/12/11/P11003
 被引用回数：8 パーセンタイル：17(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 $$gamma$$-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$$^8$$ns$$^{-1}$$cm$$^{-2}$$ 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$$_{3}$$:(Ce) detectors from the FATIMA collaboration.

論文

Development of a hybrid ECT sensor for JSFR SG double-wall tubes

山口 智彦; Mihalache, O.

Journal of Nuclear Science and Technology, 54(11), p.1201 - 1214, 2017/11

https://doi.org/10.1080/00223131.2017.1359116
 パーセンタイル：100(Nuclear Science & Technology)

A new design has been adopted for the steam generators (SG) tubes of the Japan Sodium-cooled Fast Reactor (JSFR) using double-wall tubes. This paper estimates and assesses the effectiveness of detecting defects in SG double-wall tubes of the JSFR by using combined high-frequency eddy current testing (ECT) and low-frequency remote field eddy current (RF-ECT) sensors. We confirm that the proposed hybrid ECT sensor is highly sensitive to small defects, fatigue cracks, and other defects even when located under support plates of tubes. The parameters of the hybrid ECT sensor are designed and optimized to detect small defects using accurate numerical simulations based on the finite element method (FEM), using an in-house developed code. The sensitivity and high performance of the hybrid ECT sensor was validated with experimental measurements.

論文

Study of fission using multi-nucleon transfer reactions

西尾 勝久; 廣瀬 健太郎; L$'e$guillon, R.*; 牧井 宏之; Orlandi, R.; 塚田 和明; Smallcombe, J.*; 千葉 敏*; 有友 嘉浩*; 田中 翔也*; et al.

Proceedings of 6th International Conference on Fission and Properties of Neutron-rich Nuclei (ICFN-6), p.590 - 597, 2017/11

https://doi.org/10.1142/9789813229426_0101

We are promoting a fission study using multi-nucleon transfer reactions, where excited states in neutron-rich actinide nuclei, which cannot be accessed by particle capture and/or fusion reactions, are populated. This allows us to study fission in the new region of chart of nuclei. Also, the excited states in the fissioning nucleus are widely populated in the reactions, thus the effects of excitation energy on fission can be investigated. Experiments were carried out at the JAEA tandem facility in Tokai, Japan. We studied reactions using the $$^{18}$$O beam ($$sim$$9MeV/u) and several actinide target nuclei such as $$^{232}$$Th, $$^{238}$$U, $$^{237}$$Np, $$^{248}$$Cm. Ejectile nuclei and thus the transfer channels were identified by a newly developed silicon $$Delta$$E-E detectors. The produced nuclei in one experiment reached more than fifteen. Fission fragment mass distributions (FFMDs) were measured for each isotopes. Measured FFMDs are reproduced by a calculation based on the fluctuation-dissipation model (Langevin-type calculation), where effects of multi-chance fission were included. We also started to measure the prompt neutrons accompanied by fission.

論文

Atomically dispersed Pt on the surface of Ni particles; Synthesis and catalytic function in hydrogen generation from aqueous ammonia-borane

Li, Z.*; He, T.*; 松村 大樹; Miao, S.*; Wu, A.*; Liu, L.*; Wu, G.*; Chen, P.*

ACS Catalysis, 7(10), p.6762 - 6769, 2017/10

https://doi.org/10.1021/acscatal.7b01790

We report herein that the single-atom alloy (SAA) made of atomically dispersed Pt on the surface of Ni particles (Pt is surrounded by Ni atoms) exhibits improved catalytic activity on the hydrolytic dehydrogenation of ammonia-borane, a promising hydrogen storage method for onboard applications. Specifically, an addition of 160 ppm of Pt leads to ca. 3-fold activity improvement in comparison to that of pristine Ni/CNT catalyst. The turnover frequency based on the isolated Pt is 12000 mol$$_{rm{H}2}$$ mol$$_{rm{Pt}}$$$$^{-1}$$ min$$^{-1}$$, which is about 21 times the value of the best Pt-based catalyst ever reported. Our simulation results indicate that the high activity achieved stems from the synergistic effect between Pt and Ni, where the negatively charged Pt (Pt$$^{delta -}$$) and positively charged Ni (Ni$$^{delta +}$$) in the Pt-Ni alloy are prone to interact with H and OH of H$$_{2}$$O molecules, respectively, leading to an energetically favorable reaction pathway.

論文

Measurement of high-energy prompt $$gamma$$-rays from neutron induced fission of U-235

牧井 宏之; 西尾 勝久; 廣瀬 健太郎; Orlandi, R.; L$'e$guillon, R.; 小川 達彦; Soldner, T.*; Hambsch, F.-J.*; Astier, A.*; Pollitt, A.*; et al.

EPJ Web of Conferences (Internet), 146, p.04036_1 - 04036_4, 2017/09

https://doi.org/10.1051/epjconf/201714604036
 被引用回数：2 パーセンタイル：4.05

核分裂に伴い放出される即発$$gamma$$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$$^{252}$$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$$gamma$$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$$^{252}$$Cfの自発核分裂以外で即発$$gamma$$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$$^{235}$$U(n,f)においても20MeVまでの即発$$gamma$$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。

論文

Experimental fission study using multi-nucleon transfer reactions

西尾 勝久; 廣瀬 健太郎; L$'e$guillon, R.*; 牧井 宏之; Orlandi, R.; 塚田 和明; Smallcombe, J.*; 千葉 敏*; 有友 嘉浩*; 田中 翔也*; et al.

EPJ Web of Conferences (Internet), 146, p.04009_1 - 04009_6, 2017/09

https://doi.org/10.1051/epjconf/201714604009
 被引用回数：2 パーセンタイル：4.05

The objective of this work is to extend fission data for actinide nuclei not investigated so far in order to understand the fission mechanism, especially for neutron-rich nuclei. Multi-nucleon transfer reactions were used to populate the compound nuclei which cannot be accessed by particle capture or fusion reactions. The experiment was carried out at the tandem facility of Japan Atomic Energy Agency. In the multi-nucleon transfer reactions using $$^{18}$$O beam, a wide variety of nuclei around a target nucleus was produced. By identifying transfer channels, fission data of nuclei more than fifteen compound nuclei were generated in one experiment. Another feature of transfer reaction is that the excitation energies of a compound nucleus can be populated continuously from the ground state up to several tens MeV, allowing us to study the excitation energy dependence of fission properties. From the excitation function of fission probabilities, fission-barrier heights of neutron-rich actinide nuclei were obtained. Experiments were carried out in the reactions of $$^{18}$$O + $$^{238}$$U, $$^{232}$$Th, $$^{248}$$Cm, $$^{237}$$Np. The obtained fission fragment mass distributions were reproduced by a model calculation based on a fluctuation dissipation model.

論文

R&D of multi-frequency ECT algorithms for FBR SG tubes

Mihalache, O.; 山口 智彦; 白濱 卓馬; 上田 雅司

E-Journal of Advanced Maintenance (Internet), 9(2), p.60 - 65, 2017/08

The adherence of sodium on the external surface of steam generator tubes (SGs) of Fast Breeder Reactors (FBR) adds an additional level of complexity in the in-service inspection (ISI) of SGs using eddy current testing (ECT). The paper focusses on research and development (R&D) of novel multi-frequency (MF) algorithms, based on ECT signals, special developed and tuned to enhance the signal from defects located on external SG tube surface and to suppress electromagnetic noise from the conductive sodium and SG support plates. The application of the MF algorithm is investigated using both three-dimensional finite element (FEM) simulations and experimental measurements from SG tubes soaked and then drained of sodium, in a sodium tank mock-up.

論文

Shape evolution in neutron-rich krypton isotopes beyond N=60; First spectroscopy of $$^{98,100}$$Kr

Flavigny, F.*; Doornenbal, P.*; Obertelli, A.*; Delaroche, J.-P.*; Girod, M.*; Libert, J.*; Rodriguez, T. R.*; Authelet, G.*; Baba, H.*; Calvet, D.*; et al.

Physical Review Letters, 118(24), p.242501_1 - 242501_6, 2017/06

https://doi.org/10.1103/PhysRevLett.118.242501
 被引用回数：14 パーセンタイル：9.07(Physics, Multidisciplinary)

The first $$gamma$$-ray spectroscopy of very neutron rich $$^{98,100}$$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 $$^{99,101}$$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.

論文

Second-order structural transition in (Ca$$_{0.5}$$Sr$$_{0.5}$$)$$_3$$Rh$$_4$$Sn$$_{13}$$

Cheung, Y. W.*; Hu, Y. J.*; Goh, S. K.*; 金子 耕士; 筒井 智嗣; Logg, P. W.*; Grosche, F. M.*; 金川 響*; 谷奥 泰明*; 今井 正樹*; et al.

Journal of Physics; Conference Series, 807(3), p.032002_1 - 032002_4, 2017/04

BB2016-0329.pdf:0.86MB

https://doi.org/10.1088/1742-6596/807/3/032002

(Ca$$_{0.5}$$Sr$$_{0.5}$$)$$_3$$Rh$$_4$$Sn$$_{13}$$ is a member of the substitution series (Ca$$_{x}$$Sr$$_{1-x}$$)$$_3$$Rh$$_4$$Sn$$_{13}$$ which has recently been argued to feature a structural quantum critical point at $$x_c$$ = 0.9. In the stoichiometric compound Sr$$_{3}$$Rh$$_{4}$$Sn$$_{13}$$, the structural transition at $$T^*$$ $$approx$$ 138 K has been shown to be a second-order phase transition. Moving towards xc, we examine the character of the structural transition in (Ca$$_{0.5}$$Sr$$_{0.5}$$)$$_3$$Rh$$_4$$Sn$$_{13}$$ (i.e. $$x$$ = 0.5, $$T^*$$ $$approx$$ 55 K) using electrical resistivity, heat capacity and X-ray scattering. The absence of the thermal hysteresis in specific heat around $$T^*$$, and the continuous evolution of the superlattice reflection detected by X-ray diffraction are consistent with the scenario that the structural transition associated with a modulation vector $$q$$ = (0.5, 0.5, 0) in (Ca$$_{0.5}$$Sr$$_{0.5}$$)$$_3$$Rh$$_4$$Sn$$_{13}$$ remains second-order on approaching the quantum critical point.

論文

Magnetization dynamics and its scattering mechanism in thin CoFeB films with interfacial anisotropy

岡田 篤*; He, S.*; Gu, B.; 金井 駿*; Soumyanarayanan, A.*; Lim, S. T.*; Tran, M.*; 森 道康; 前川 禎通; 松倉 文礼*; et al.

Proceedings of the National Academy of Sciences of the United States of America, 144(15), p.3815 - 3820, 2017/04

http://doi.org/10.1073/pnas.1613864114

Studies of magnetization dynamics have incessantly facilitated the discovery of fundamentally novel physical phenomena, making steady headway in the development of magnetic and spintronics devices. The dynamics can be induced and detected electrically, offering new functionalities in advanced electronics at the nanoscale. However, its scattering mechanism is still disputed. Understanding the mechanism in thin films is especially important, because most spintronics devices are made from stacks of multilayers with nanometer thickness. The stacks are known to possess interfacial magnetic anisotropy, a central property for applications, whose influence on the dynamics remains unknown. Here, we investigate the impact of interfacial anisotropy by adopting CoFeB/MgO as a model system. Through systematic and complementary measurements of ferromagnetic resonance (FMR) on a series of thin films, we identify narrower FMR linewidths at higher temperatures. We explicitly rule out the temperature dependence of intrinsic damping as a possible cause, and it is also not expected from existing extrinsic scattering mechanisms for ferromagnets. We ascribe this observation to motional narrowing, an old concept so far neglected in the analyses of FMR spectra. The effect is confirmed to originate from interfacial anisotropy, impacting the practical technology of spin-based nanodevices up to room temperature.

論文

Identification of the crossing point at $$N$$ = 21 between normal and intruder configurations

Lic$u{a}$, R.*; Rotaru, F.*; Borge, M. J. G.*; Gr$'e$vy, S.*; Negoita, F.*; Poves, A.*; Sorlin, O.*; Andreyev, A.; Borcea, R.*; Costache, C.*; et al.

Physical Review C, 95(2), p.021301_1 - 021301_6, 2017/02

https://doi.org/10.1103/PhysRevC.95.021301
 被引用回数：6 パーセンタイル：18.72(Physics, Nuclear)

The $$beta^{-}$$ decay of $$^{34}$$Mg was used to study the $$^{34}$$Al nucleus through $$gamma$$ spectroscopy at the Isotope Separator On-Line facility of CERN. Previous studies identified two $$beta$$-decaying states in $$^{34}$$Al having spin-parity assignments $$J^{pi}$$=4$$^{-}$$ dominated by the normal configuration $$pi$$(d5/2)$$^{-1}$$ $$bigoplus$$ $$nu$$(f7/2) and $$J^{pi}$$ = 1$$^{+}$$ by the intruder configuration $$pi$$(d5/2)$$^{-1}$$ $$bigoplus$$ $$nu$$(d3/2)$$^{-1}$$(f7/2)$$^{2}$$. Their unknown ordering and relative energy have been the subject of debate for the placement of $$^{34}$$Al inside or outside the $$N$$ = 20 "island of inversion". We report here that the 1$$^{+}$$ intruder lies only 46.6 keV above the 4$$^{-}$$ ground state. In addition, a new half-life of $$T_{1/2}$$=44.9(4)ms, that is twice as long as thepreviously measured 20(10) ms, has been determined for $$^{34}$$Mg. Large-scale shell-model calculations with the recently developed SDPF-U-MIX interaction are compared with the new data and used to interpret the mechanisms at play at the very border of the $$N$$ = 20 island of inversion.

論文

Changes in mean-squared charge radii and magnetic moments of $$^{179-184}$$Tl measured by in-source laser spectroscopy

Barzakh, A.*; Andreyev, A.; Cocolios, T. E.*; de Groote, R. P.*; Fedorov, D. V.*; Fedosseev, V. N.*; Ferrer, R.*; Fink, D. A.*; Ghys, L.*; Huyse, M.*; et al.

Physical Review C, 95(1), p.014324_1 - 014324_12, 2017/01

https://doi.org/10.1103/PhysRevC.95.014324
 被引用回数：10 パーセンタイル：8.11(Physics, Nuclear)

Hyperfine structure and isotope shifts have been measured for the ground and isomeric states in the neutron deficient isotopes $$^{179-184}$$Tl using the 276.9 nm transition. The experiment has been performed at the CERN Isotope Separator On-Line facility using the in-source resonance-ionization laser spectroscopy technique. Spins for the ground states in $$^{179,181,183}$$Tl have been determined as $$I$$ = 1/2. Magnetic moments and changes in the nuclear mean-square charge radii have been deduced. By applying the additivity relation for magnetic moments of the odd-odd Tl nuclei the leading configuration assignments were confirmed. A deviation of magnetic moments for isomeric states in $$^{182,184}$$Tl from the trend of the heavier Tl nuclei is observed. The charge radii of the ground states of the isotopes $$^{179-184}$$Tl follow the trend for isotonic (spherical) lead nuclei. The noticeable difference in charge radii for ground and isomeric states of $$^{183,184}$$Tl has been observed, suggesting a larger deformation for the intruder-based 9/2$$^{-}$$ and 10$$^{-}$$ states compared to the ground states. An unexpected growth of the isomer shift for $$^{183}$$Tl has been found.

論文

Are there signatures of harmonic oscillator shells far from stability?; First spectroscopy of $$^{110}$$Zr

Paul, N.*; Corsi, A.*; Obertelli, A.*; Doornenbal, P.*; Authelet, G.*; Baba, H.*; Bally, B.*; Bender, M.*; Calvet, D.*; Ch$^a$teau, F.*; et al.

Physical Review Letters, 118(3), p.032501_1 - 032501_7, 2017/01

https://doi.org/10.1103/PhysRevLett.118.032501
 被引用回数：14 パーセンタイル：9.07(Physics, Multidisciplinary)

The first measurement of $$gamma$$ rays emitted by the very neutron rich nuclei $$^{112}$$Mo (Z=42) and $$^{110}$$Zr (Z=40) was carried out at the RIBF facility at RIKEN. These data shine light on the postulated N=70 harmonic oscillator shell. If the spin-orbit splitting which gives rise to the N=82 shell gap is reduced in very neutron-rich nuclei, the harmonic oscillator gap at N=70 should open instead. However, both the measured energy of the first excited state $$^{112}$$Mo and $$^{110}$$Zr, respectively 235(7) keV and 185(11) keV, and their E(4$$^+$$)/E(2$$^+$$) ratio, indicate that these nuclei are good rotors, and exclude the shell stabilization scenario at Z=40 and N=70. These results were compared to state-of-the-art density functional theoretical calculations using Gogny and Skyrme effective interactions.

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