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論文

The BCC $$rightarrow$$ FCC hierarchical martensite transformation under dynamic impact in FeMnAlNiTi alloy

Li, C.*; Fang, W.*; Yu, H. Y.*; Peng, T.*; Yao, Z. T.*; Liu, W. G.*; Zhang, X.*; 徐 平光; Yin, F.*

Materials Science & Engineering A, 892, p.146096_1 - 146096_11, 2024/02

The quasi-static superelastic responses and hierarchical martensite transformation from body-centered cubic (BCC) to face-centered cubic (FCC) under dynamic impact in Fe$$_{42}$$Mn$$_{34}$$Al$$_{15}$$Ni$$_{7.5}$$Ti$$_{1.5}$$ alloys were investigated. Polycrystalline and oligocrystalline alloys were produced through solution heat treatment and cyclic heat treatment processes, respectively. The results show the volume fraction of residual martensite for oligocrystalline alloys is lower, which exhibits better superelastic responses compared with polycrystalline alloys. Dynamic impact tests indicate that, despite the weakening of the grain boundary strengthening effect, the ultimate strength of the oligocrystalline alloys closely matches that of the polycrystalline alloys under dynamic impact. The martensite transformation of the FeMnAlNiTi alloy is characterized as hierarchical under dynamic impact, and increasing strain rates and grain sizes can enhance the BCC $$rightarrow$$ FCC martensite transformation, resulting in higher martensite phase fractions for oligocrystalline alloys. The increase in ultimate strength is attributed to the dynamic Hall-Petch effect introduced by more martensite phase interfaces under dynamic impact.

論文

Probing deformation behavior of a refractory high-entropy alloy using ${it in situ}$ neutron diffraction

Zhou, Y.*; Song, W.*; Zhang, F.*; Wu, Y.*; Lei, Z.*; Jiao, M.*; Zhang, X.*; Dong, J.*; Zhang, Y.*; Yang, M.*; et al.

Journal of Alloys and Compounds, 971, p.172635_1 - 172635_7, 2024/01

The grain orientation-dependent lattice strain evolution of a (TiZrHfNb)$$_{98}$$$$N_2$$ refractory high-entropy alloy (HEA) during tensile loading has been investigated using ${it in situ}$ neutron diffraction. The equivalent strain-hardening rate of each of the primary $$<hkl>$$-oriented grain families was found to be relatively low, manifesting the macroscopically weak work-hardening ability of such a body-centered cubic (BCC)-structured HEA. This finding is indicative of a dislocation planar slip mode that is confined in a few single-slip planes and leads to in-plane softening by high pile-up stresses.

論文

Grain size independence of cryogenic strain recovery behavior in high-Zr $$beta$$-Ti alloy

Zhang, B.*; Xin, S.*; Huang, M.*; Mao, W.; Jia, W.*; Li, Q.*; Li, S.*; Zhang, S.*; Mao, C.*

Materials Science & Engineering A, 890, p.145898_1 - 145898_7, 2024/01

本研究では、高Zr-$$beta$$-Ti合金の変形温度を300Kから77Kに下げると回復ひずみが2.25%から5.5%に大幅に増加することを報告した。この合金の超弾性は77Kにおいて$$beta$$粒径に依存しないことがわかった。その結果、粗粒試料は77Kで超微粒試料とほぼ同じ超弾性を示すことがわかった。変形誘起マルテンサイト変態と転位すべりの相対的な容易さは77Kで大きく変化し、転位すべりは強く抑制され、超弾性に対する結晶粒の微細化の影響は影を潜めた。

論文

Tetrahedral triple-Q magnetic ordering and large spontaneous Hall conductivity in the metallic triangular antiferromagnet Co$$_{1/3}$$TaS$$_{2}$$

Park, P.*; Cho, W.*; Kim, C.*; An, Y.*; Kang, Y.-G.*; Avdeev, M.*; Sibille, R.*; 飯田 一樹*; 梶本 亮一; Lee, K. H.*; et al.

Nature Communications (Internet), 14, p.8346_1 - 8346_9, 2023/12

The triangular lattice antiferromagnet (TLAF) has been the standard paradigm of frustrated magnetism for several decades. The most common magnetic ordering in insulating TLAFs is the 120$$^{circ}$$ structure. However, a new triple-$$mathbf{Q}$$ chiral ordering can emerge in metallic TLAFs, representing the short wavelength limit of magnetic skyrmion crystals. We report the metallic TLAF Co$$_{1/3}$$TaS$$_{2}$$ as the first example of tetrahedral triple-$$mathbf{Q}$$ magnetic ordering with the associated topological Hall effect (non-zero $$sigma_{xy}(mathbf{H}=0)$$). We also present a theoretical framework that describes the emergence of this magnetic ground state, which is further supported by the electronic structure measured by angle-resolved photoemission spectroscopy. Additionally, our measurements of the inelastic neutron scattering cross section are consistent with the calculated dynamical structure factor of the tetrahedral triple-$$mathbf{Q}$$ state.

論文

Direct observation of topological magnon polarons in a multiferroic material

Bao, S.*; Gu, Z.-L.*; Shangguan, Y.*; Huang, Z.*; Liao, J.*; Zhao, X.*; Zhang, B.*; Dong, Z.-Y.*; Wang, W.*; 梶本 亮一; et al.

Nature Communications (Internet), 14, p.6093_1 - 6093_9, 2023/09

Magnon polarons are novel elementary excitations possessing hybrid magnonic and phononic signatures, and are responsible for many exotic spintronic and magnonic phenomena. Despite long-term sustained experimental efforts in chasing for magnon polarons, direct spectroscopic evidence of their existence is hardly observed. Here, we report the direct observation of magnon polarons using neutron spectroscopy on a multiferroic Fe$$_{2}$$Mo$$_{3}$$O$$_{8}$$ possessing strong magnon-phonon coupling. Specifically, below the magnetic ordering temperature, a gap opens at the nominal intersection of the original magnon and phonon bands, leading to two separated magnon-polaron bands. Each of the bands undergoes mixing, interconverting and reversing between its magnonic and phononic components. We attribute the formation of magnon polarons to the strong magnon-phonon coupling induced by Dzyaloshinskii-Moriya interaction. Intriguingly, we find that the band-inverted magnon polarons are topologically nontrivial. These results uncover exotic elementary excitations arising from the magnon-phonon coupling, and offer a new route to topological states by considering hybridizations between different types of fundamental excitations.

論文

A Predicted CRISPR-mediated symbiosis between uncultivated archaea

Esser, S. P.*; Rahlff, J.*; Zhao, W.*; Predl, M.*; Plewka, J.*; Sures, K.*; Wimmer, F.*; Lee, J.*; Adam, P. S.*; McGonigle, J.*; et al.

Nature Microbiology (Internet), 8(9), p.1619 - 1633, 2023/09

 被引用回数:1 パーセンタイル:68.07

CRISPR-Cas systems defend prokaryotic cells from viruses, plasmids, and other mobile genetic elements. Capitalizing on multi-omics approaches, we show here that the CRISPR-Cas systems of uncultivated archaea also play an integral role in mitigating potentially detrimental interactions with episymbionts. A comprehensive analysis of CRISPR-Cas-based infection histories revealed that uncultivated deep-subsurface archaeal primary-producers defend themselves from archaeal episymbionts of the DPANN superphylum of archaea, some of which are known to fuse their membranes with their host. We show that host cells counter these attacks by deploying one of two CRISPR-Cas systems (type I-B and type III-A) to target and disrupt essential genes in the episymbiont. However, genome-scale modeling of metabolic interactions between two deep subsurface host-symbiont systems revealed that host cells also benefit from the symbionts via metabolic complementation. We speculate that populations of these uncultivated archaeal episymbionts are currently transitioning from a parasitic lifestyle to one of mutualism, as must have occurred in countless mutualistic systems known today. By expanding our analysis to thousands of archaeal genomes, we conclude that CRISPR-Cas mediated resistance to archaeal episymbiosis evolved independently in various archaeal lineages and may be a wide-spread evolutionary phenomenon.

論文

${it In situ}$ neutron diffraction study on the deformation behavior of the plastic inorganic semiconductor Ag$$_{2}$$S

Wang, Y.*; Gong, W.; 川崎 卓郎; Harjo, S.; Zhang, K.*; Zhang, Z. D.*; Li, B.*

Applied Physics Letters, 123(1), p.011903_1 - 011903_6, 2023/07

 被引用回数:0 パーセンタイル:0

Bulk Ag$$_{2}$$S is a plastic inorganic semiconductor at room temperature. It exhibits a compressive strain greater than 50%, which is highly different from brittle conventional counterparts, such as silicon. Here, we present the experimental investigation of the deformation behavior in a plastic inorganic semiconductor Ag$$_{2}$$S using ${it in situ}$ neutron diffraction during compressive deformation at room and elevated temperatures. At room temperature, the lattice strain partitioning among $$hkl$$-orientated grain families could be responsible for the significant work-hardening behavior in the bulk Ag$$_{2}$$S with a monoclinic structure. The rapid accumulation of lattice defects and remarkable development of the deformation texture suggest that dislocation slip promotes plasticity. At 453 K, a monoclinic phase transforms into a body-centered cubic phase. A stress plateau appears at $$sim$$-4.8 MPa, followed by a rehardening state. The deformation mode of bulk Ag$$_{2}$$S at the initial stage is likely attributable to the migration of silver ions, and as strain increases, it is closer to that of room temperature, leading to rehardening.

論文

A Large-scale particle-based simulation of heat and mass transfer behavior in EAGLE ID1 in-pile test

Zhang, T.*; Yao, Y.*; 守田 幸路*; Liu, X.*; Liu, W.*; 今泉 悠也; 神山 健司

Proceedings of 30th International Conference on Nuclear Engineering (ICONE30) (Internet), 9 Pages, 2023/05

The in-pile EAGLE ID1 test was conducted by Japan Atomic Energy Agency to demonstrate the effectiveness of the fuel assembly with an internal duct structure during a core disruptive accident in a sodium-cooled fast reactor. In this study, a new computational fluid dynamics code based on the fully Lagrangian particle method was developed for the purpose of clarifying the failure mechanism of the inner duct wall of FAIDUS. The three-dimensional simulation of the ID1 test was performed to analyze a series of thermal hydraulic behaviors leading up to duct wall failure for a computational domain that included six fuel pins. The simulations reasonably reproduced the heat transfer characteristics observed in the test, showing that the local contact of liquid steel with high thermal conductivity with the duct wall greatly enhances the heat transfer from the nuclear heating fuel to the duct wall. The results support the validity of the conclusions of our analytical study regarding the molten pool-to-duct wall heat transfer mechanism that caused the thermal failure of the duct wall.

論文

A Colossal barocaloric effect induced by the creation of a high-pressure phase

Jiang, X.*; 服部 高典; Xu, X.*; Li, M.*; Yu, C.*; Yu, D.*; Mole, R.*; 矢野 真一郎*; Chen, J.*; He, L.*; et al.

Materials Horizons, 10(3), p.977 - 982, 2023/03

 被引用回数:1 パーセンタイル:92.54(Chemistry, Multidisciplinary)

現在の蒸気圧縮式冷凍機に代わる環境に優しい冷凍機として、バロカロリック効果に基づく固体冷凍機が世界的に注目されている。一般に、バロカロリック効果が発現する相はいずれも常圧でも存在する。ここでは、それらの物質と違って、KPF$$_{6}$$が高圧の菱面体晶相を生成することにより、巨大なバロカロリック効果を示すことを実証した。相図は、圧力依存の熱量測定、ラマン散乱測定、中性子回折測定に基づいて構築されたものである。本研究は、巨大バロカロリー効果に、高圧相の生成という新たな手法をもたらすと期待される。

論文

Tensile overload-induced texture effects on the fatigue resistance of a CoCrFeMnNi high-entropy alloy

Lam, T.-N.*; Chin, H.-H.*; Zhang, X.*; Feng, R.*; Wang, H.*; Chiang, C.-Y.*; Lee, S. Y.*; 川崎 卓郎; Harjo, S.; Liaw, P. K.*; et al.

Acta Materialia, 245, p.118585_1 - 118585_9, 2023/02

 被引用回数:2 パーセンタイル:62.4(Materials Science, Multidisciplinary)

The present study investigates the crystallographic-texture effects on the improved fatigue resistance in the CoCrFeMnNi high-entropy alloys (HEAs) with the full-size geometry of the ASTM Standards E647-99. We exploited X-ray nano-diffraction mapping to characterize the crystal-deformation levels ahead of the crack tip after stress unloading under both constant- and tensile overloaded-fatigue conditions. The crack-tip blunting-induced much higher deformation level was concentrated surrounding the crack-tip which delays the fatigue-crack growth immediately after a tensile overload. The predominant deformation texture orientation in the Paris regime was investigated, using electron backscatter diffraction and orientation distribution function analyses. The twinning formation-driven shear deformation gave rise to the development of the Goss-type texture within the plastic deformation regime under a tensile-overloaded-fatigue condition, which was attributed to enhance the crack deflection and thus the tensile induced crack-growth-retardation period in the CoCrFeMnNi HEA.

論文

Grain refinement in titanium prevents low temperature oxygen embrittlement

Chong, Y.*; Gholizadeh, R.*; 都留 智仁; Zhang, R.*; 井上 耕治*; Gao, W.*; Godfrey, A.*; 光原 昌寿*; Morris, J. W. Jr.*; Minor, A. M.*; et al.

Nature Communications (Internet), 14, p.404_1 - 404_11, 2023/02

 被引用回数:1 パーセンタイル:92.54

チタンは格子間酸素によって脆化する。特に極低温では顕著な脆化挙動を示すため、チタンやその合金の製造において酸素含有量を厳しく管理する必要がある。この問題を解決するために、我々は結晶粒の微細化という構造戦略を提案した。77Kで非常に脆い粗粒の組織と比較して、Ti-0.3wt.%Oの超微細粒(UFG)組織(粒径$$sim$$2.0$$mu$$m)は、UFG組織特有の超高降伏強度を維持したまま均一延びを1桁上昇させることに成功した。UFG Ti-0.3wt.%Oにおけるこの特異な強度-延性相乗効果は、粒界凝集エネルギー向上に寄与する希薄な酸素の粒界偏析と優れたひずみ硬化能に寄与する$$<c+a>$$転位の活性化の複合効果によって達成された。この方法は、低温での高強度Ti-O合金の応用の可能性を高めるだけでなく、格子間固溶硬化による延性の低下を生じる他の合金系にも適用できる可能性がある。

論文

Hybridized propagation of spin waves and surface acoustic waves in a multiferroic-ferromagnetic heterostructure

Chen, J.*; 山本 慧; Zhang, J.*; Ma, J.*; Wang, H.*; Sun, Y.*; Chen, M.*; Ma, J.*; Liu, S.*; Gao, P.*; et al.

Physical Review Applied (Internet), 19(2), p.024046_1 - 024046_9, 2023/02

 被引用回数:1 パーセンタイル:94.06(Physics, Applied)

Coherent coupling in magnon based hybrid system has many potential applications in quantum information processing. Magnons can propagate in magnetically ordered materials without any motion of electrons, offering a unique method to build low-power-consumption devices and information channels free of heat dissipation. In this article, we demonstrate the coherent propagation of hybridized modes between spin waves and Love surface acoustic waves in a multiferroic BiFeO$$_{3}$$ and ferromagnetic La$$_{0.67}$$Sr$$_{0.33}$$MnO$$_{3}$$ based heterostructure. The magneto-elastic coupling enables a giant enhancement of strength of the hybridized mode by a factor of 26 compared to that of the pure spin waves. A short wavelength down to 250 nm is demonstrated for the hybridized mode, which is desirable for nanoscale acousto-magnonic applications. Our combined experimental and theoretical analyses represent an important step towards the coherent control in hybrid magnonics, which may inspire the study of magnon-phonon hybrid systems for coherent information processing and manipulation.

論文

Fatigue crack non-propagation behavior of a gradient steel structure from induction hardened railway axles

Zhang, H.*; Wu, S. C.*; Ao, N.*; Zhang, J. W.*; Li, H.*; Zhou, L.*; 徐 平光; Su, Y. H.

International Journal of Fatigue, 166, p.107296_1 - 107296_11, 2023/01

 被引用回数:0 パーセンタイル:84.8(Engineering, Mechanical)

Abnormal damages in railway axles can lead to a significant hazard to running safety and reliability. To this end, a surface treatment was selected to effectively inhibit fatigue crack initiation and growth. In this study, a single edge notch bending fatigue test campaign with artificial notches was conducted to elucidate the fatigue crack non-propagation behavior in railway S38C axles subjected to an induction hardening process. The fatigue cracking behavior in the gradient structure was revealed by optical microscopy, electron backscatter diffraction, and fractography. The microhardness distribution was measured using a Vickers tester. The obtained results show that the microhardness of the strengthening layer is nearly triple that of the matrix. Owing to the gradient microstructures and hardness, as well as compressive residual stress, the fatigue long crack propagates faster once it passes through the hardened zone (approximately 2.0 mm in the radial depth). Thereafter, local retarding (including deflection, branching, and blunting) of the long crack occurs because of the relatively coarse ferrite and pearlite in the transition region and matrix. Totally, this fatigue cracking resistance is reasonably believed to be due to the gradient microstructure and residual stress. These findings help to tailor a suitable detection strategy for maximum defects or cracks in railway axles.

論文

Experimental evidence for the significance of optical phonons in thermal transport of tin monosulfide

Wu, P.*; 村井 直樹; Li, T.*; 梶本 亮一; 中村 充孝; 古府 麻衣子; 中島 健次; Xia, K.*; Peng, K.*; Zhang, Y.*; et al.

New Journal of Physics (Internet), 25(1), p.013032_1 - 013032_11, 2023/01

 被引用回数:0 パーセンタイル:0(Physics, Multidisciplinary)

The understanding of the lattice dynamics is essential for engineering the thermal transport properties in quantum materials. Based on the canonical point of view, acoustic phonons are believed to be the principal thermal carriers in heat flow. Here, in this work, optical phonons are elucidated to play a pivotal role in determining the lattice thermal conductivity in thermoelectric material SnS by using the state-of-the-art inelastic neutron scattering technique combined with first-principles calculations. Additionally, in contrast to acoustic phonons, optical phonons are observed to exhibit pronounced softening and broadening with temperature. Our observations not only shed light on the significance of the optical phonons in thermal transport but also provide a vital clue to suppress the propagation of optical phonons to optimize the thermoelectric performance of SnS.

論文

A 3D particle-based simulation of heat and mass transfer behavior in the EAGLE ID1 in-pile test

Zhang, T.*; 守田 幸路*; Liu, X.*; Liu, W.*; 神山 健司

Annals of Nuclear Energy, 179, p.109389_1 - 109389_10, 2022/12

 被引用回数:1 パーセンタイル:35.78(Nuclear Science & Technology)

The ID1 test was the final target test of the EAGLE experimental framework program. It was used to verify that during a core disruptive accident, the molten fuel could be discharged via wall failure of an inner duct in FAIDUS, a design concept for the sodium-cooled fast reactor. The ID1 results revealed that the wall failure behavior owed to the large heat flow from the surrounding fuel/steel mixture. The present study numerically investigated the heat transfer mechanisms in the test using the finite volume particle method in the three-dimensional domain. The thermal hydraulic behaviors during wall failure were reproduced reasonably. The present three-dimensional simulation mitigated inherent defects of our previous two-dimensional calculation and clarified that the solid fuel and liquid steel close to the outer surface of the duct can expose the duct to high thermal loads, resulting in the wall failure.

論文

Ten years of warming increased plant-derived carbon accumulation in an East Asian monsoon forest

Zhang, J.*; Kuang, L.*; Mou, Z.*; 近藤 俊明*; 小嵐 淳; 安藤 麻里子; Li, Y.*; Tang, X.*; Wang, Y.-P.*; Pe$~n$uelas, J.*; et al.

Plant and Soil, 481(1-2), p.349 - 365, 2022/12

 被引用回数:0 パーセンタイル:26.86(Agronomy)

Soil warming effects on soil organic carbon (SOC) decomposition and stabilization are highly variable, and the underlying mechanisms are poorly understood. In this study, concentration, stability (dissolved, particle and mineral-associated SOC), and source (plant-derived and microbial-derived) of SOC, soil microbial community composition, and enzyme activities were studied in a 10-year soil warming field experiment in an East Asian monsoon forest. The results showed that 10-year soil warming significantly enhanced SOC in the top 0-10 cm soil. The increased SOC induced by warming was mainly derived from plants with lignin markers, accompanied by a decrease in microbial-derived SOC. This highlights an urgent need for a better understanding of how the contrasting effects of plant- and microbial-derived C mediate the response of the SOC pool to warming across different biomes.

論文

First observation of the decay of the 13/2$$^+$$ isomer in $$^{183}$$Hg and $$B$$(${it M}$2) systematics of neutron transitions across the nuclear chart

Huang, H.*; Zhang, W. Q.*; Andreyev, A. N.; Liu, Z.*; Seweryniak, D.*; Li, Z. H.*; Guo, C. Y.*; Barzakh, A. E.*; Van Duppen, P.*; Andel, B.*; et al.

Physics Letters B, 833, p.137345_1 - 137345_8, 2022/10

 被引用回数:0 パーセンタイル:0.02(Astronomy & Astrophysics)

The decay of the 13/2$$^+$$ isomeric state in $$^{183}$$Hg was observed for the first time following the $$alpha$$ decay of the 13/2$$^+$$ isomer in $$^{187}$$Pb produced in the $$^{142}$$Nd$$(^{50}$$Cr$$, 2p3n)$$ reaction. Using $$alpha$$-$$gamma$$ delayed coincidence measurements, the half-life of this isomer was measured to be 290(30) $$mu$$s. This isomer is proposed to deexcite by an unobserved low-energy $$M$$2 transition to the known 9/2$$^-$$ member of a strongly prolate-deformed 7/2$$^-$$[514] band, followed by a 105-keV $$M$$1 transition to the bandhead. A lower limit of B($$M$$2)$$geq$$0.018 W.u. was deduced for the unobserved transition. The presumed retardation is proposed to be due to the notable shape change between the initial, nearly spherical, and the final, strongly deformed, states. A similar scenario is also considered for the 13/2$$^+$$ isomer in $$^{181}$$Hg, suggesting both are cases of shape isomers. The B($$M$$2) systematics of neutron transitions across the nuclear chart is discussed.

論文

Particle-based simulation of jet impingement behaviors

高塚 大地*; 守田 幸路*; Liu, W.*; Zhang, T.*; 中村 武志*; 神山 健司

Proceedings of 12th Japan-Korea Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS12) (Internet), 10 Pages, 2022/10

A 3D particle-based simulation code was developed to analyze jet impingement behavior, and the physical models for thermal-hydraulic interactions between molten jets and solid plates used in the code was validated by simulating existing jet impingement experiments. In addition, particle-based simulations were conducted to understand the impingement characteristics of molten MOX fuel jets on SS plates, and the erosion rate of the SS plate was evaluated. The results showed that fuel crusts formed on the plate potentially provide thermal protection and confirmed the effect of the plate erosion rate on the jet diameter under conditions where crust formation is dominant.

論文

Identification of excited states in $$^{188}$$Bi and $$^{188}$$Po

Zhang, W. Q.*; Andreyev, A. N.; Liu, Z.*; Seweryniak, D.*; Huang, H.*; 他37名*

Physical Review C, 106(2), p.024317_1 - 024317_11, 2022/08

 被引用回数:1 パーセンタイル:35.31(Physics, Nuclear)

The neutron-deficient $$^{188}$$Bi and $$^{188}$$Po isotopes have been studied by $$gamma$$-ray spectroscopy using the recoil-decay tagging technique with the Argonne Gas-Filled Analyzer. A new 0.25(5)-micro second isomeric state and a prompt cascade formed by 319-, 366-, and 462-keV $$gamma$$ rays have been established on top of the (10$$^{-}$$) $$alpha$$-decaying isomer in $$^{188}$$Bi. The first excited (2$$^{+}$$) state in $$^{188}$$Po was identified, its excitation energy of 242(2) keV continues the nearly constant trend for the first 2$$^{+}$$ states in $$^{190,192,194}$$Po. The state is most likely a member of a prolate rotational band built on the ground state, albeit mixing with other coexisting configurations cannot be excluded. The new results obtained in the present work provide new information to shape coexistence in bismuth and polonium isotopes near the neutron midshell at $$N$$ = 104. In this mass region, a reduction in the prompt $$gamma$$-ray yield obtained with recoil decay tagging was observed for a few nuclides, and the possible reasons are presented.

論文

First observation of a shape isomer and a low-lying strongly-coupled prolate band in neutron-deficient semi-magic $$^{187}$$Pb

Zhang, W. Q.*; Andreyev, A. N.; Liu, Z.*; Seweryniak, D.*; Huang, H.*; Li, Z. H.*; Li, J. G.*; Guo, C. Y.*; 他34名*

Physics Letters B, 829, p.137129_1 - 137129_7, 2022/06

 被引用回数:3 パーセンタイル:79.41(Astronomy & Astrophysics)

Prompt and delayed $$gamma$$-ray spectroscopy of the neutron-deficient, semi-magic isotope $$^{187}$$Pb has been performed at the Argonne Gas-Filled Analyzer. A new 5.15(15)-$$mu$$s isomeric state at only 308 keV above the spherical 3/2$$^{-}$$ ground state is identified and classified as a shape isomer. A strongly-coupled band is observed on top of the isomer, which is nearly identical to the one built on the prolate 7/2$$^{-}$$[514] Nilsson state in the isotone $$^{185}$$Hg. Based on this similarity and on the result of the potential-energy surface calculations, the new isomer in $$^{187}$$Pb is proposed to originate from the same configuration. The retarded character of the 308-keV transition can be well explained by the significant difference between the prolate parent and spherical daughter configurations, leading to the shape isomerism. The combined results of the present work and the previous $$alpha$$-decay and laser spectroscopy studies present evidence for triple shape coexistence at low energy in the negative-parity configurations of $$^{187}$$Pb, which is well reproduced by the potential-energy surface calculations.

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