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論文

$$Q$$-dependent collective relaxation dynamics of glass-forming liquid Ca$$_{0.4}$$K$$_{0.6}$$(NO$$_{3}$$)$$_{1.4}$$ investigated by wide-angle neutron spin-echo

Luo, P.*; Zhai, Y.*; Falus, P.*; Garc$'i$a Sakai, V.*; Hartl, M.*; 古府 麻衣子; 中島 健次; Faraone, A.*; Z, Y.*

Nature Communications (Internet), 13, p.2092_1 - 2092_9, 2022/04

https://doi.org/10.1038/s41467-022-29778-4
 被引用回数：12 パーセンタイル：73.09(Multidisciplinary Sciences)

The relaxation behavior of glass formers exhibits spatial heterogeneity and dramatically changes upon cooling towards the glass transition. However, the underlying mechanisms of the dynamics at different microscopic length scales are not fully understood. We measured the $$Q$$-dependent coherent intermediate scattering function of a prototypical ionic glass former Ca$$_{0.4}$$K$$_{0.6}$$(NO$$_{3}$$)$$_{1.4}$$, in the highly viscous liquid state. In contrast to the structure modulated dynamics for $$Q$$ $$<$$ 2.4 $AA$^{-1}$$, i.e., at and below the structure factor main peak, for $$Q$$ $$>$$ 2.4 $AA$^{-1}$$, beyond the first minimum above the structure factor main peak, the stretching exponent exhibits no temperature dependence and concomitantly the relaxation time shows smaller deviations from Arrhenius behavior. This finding indicates a change in the dominant relaxation mechanisms around a characteristic length of 2.6 AA, below which the relaxation process exhibits a temperature independent distribution and more Arrhenius-like behavior.

論文

Field-tuned magnetic structure and phase diagram of the honeycomb magnet YbCl$$_3$$

Hao, Y. Q.*; Wo, H. L.*; Gu, Y. M.*; Zhang, X. W.*; Gu, Y. Q.*; Zheng, S. Y.*; Zhao, Y.*; Xu, G. Y.*; Lynn, J. W.*; 中島 健次; et al.

Science China; Physics, Mechanics & Astronomy, 64(3), p.237411_1 - 237411_6, 2021/03

https://doi.org/10.1007/s11433-020-1626-3
 被引用回数：12 パーセンタイル：69.00(Physics, Multidisciplinary)

We report thermodynamic and neutron diffraction measurements on the magnetic ordering properties of the honeycomb lattice magnet YbCl$$_3$$. We find YbCl$$_3$$ exhibits a N${'e}$el type long-range magnetic order at the wavevector (0, 0, 0) below T$$_N$$ = 600 mK. This magnetic order is associated with a small sharp peak in heat capacity and most magnetic entropy release occurs above the magnetic ordering temperature. The magnetic moment lies in-plane, parallel to the monoclinic a-axis, whose magnitude m$$_{rm Yb}$$ = 0.86(3) $$mu_B$$ is considerably smaller than the expected fully ordered moment of 2.24 $$mu_B$$ for the doublet crystal-field ground state. The magnetic ordering moment gradually increases with increasing magnetic field perpendicular to the ab-plane, reaching a maximum value of 1.6(2) $$mu_B$$ at 4 T, before it is completely suppressed above $$sim$$9 T. These results indicate the presence of strong quantum fluctuations in YbCl$$_3$$.

論文

Neutron spin-echo studies of the structural relaxation of network liquid ZnCl$$_2$$ at the structure factor primary peak and prepeak

Luo, P.*; Zhai, Y.*; Leao, J. B.*; 古府 麻衣子; 中島 健次; Faraone, A.*; Zhang, Y.*

Journal of Physical Chemistry Letters (Internet), 12(1), p.392 - 398, 2021/01

https://doi.org/10.1021/acs.jpclett.0c03146
 被引用回数：6 パーセンタイル：36.33(Chemistry, Physical)

典型的なネットワークイオン性液体ZnCl$$_2$$の第1およびプレ回折ピークでの微視的な構造緩和を中性子スピンエコー分光により調べた。第1構造ピークの緩和はプレピークのものより速く、活性化エネルギーは約33%高い。融点より十分高温においても、伸長指数関数で記述される緩和が観測された。驚くべきことに、とくに第1ピークにおいて、非指数関数性パラメータは冷却とともに急激に増加し、$$T_{rm m}$$に向かって緩和は伸長指数型から指数型へと変わる。これらの結果は、過冷却状態の典型的なガラス的ダイナミクスが平衡液体で現れること、2つの異なる空間スケールの運動の活性化エネルギーが冷却に伴うネットワーク構造の形成と関連していることを示唆する。

論文

Two inherent crossovers of the diffusion process in glass-forming liquids

古府 麻衣子; Faraone, A.*; Tyagi, M.*; 長尾 道弘*; 山室 修*

Physical Review E, 98(4), p.042601_1 - 042601_6, 2018/10

https://doi.org/10.1103/PhysRevE.98.042601
 被引用回数：7 パーセンタイル：49.04(Physics, Fluids & Plasmas)

We report on incoherent quasielastic neutron scattering measurements examining a self-diffusion process in two types of glass-forming liquids, namely a molecular liquid (3-methylpentane) and an ionic liquid (1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide). We have experimentally demonstrated that both liquids exhibit two crossovers in the momentum transfer ($$Q$$) dependence of the self-correlation function, which is basically described by the stretched exponential function, $$exp [-(t/tau)^beta]$$. The first crossover point ($$Q approx 0.2$$~$AA$^{-1}$$) corresponds to a crossover from Fickian ($$beta = 1$$) to non-Fckian ($$beta ne 1$$) diffusion attributed to dynamical correlation. On the other hand, the second one at $$Q approx 0.8$$~$AA$^{-1}$$ is associated with the crossover from Gaussian to non-Gaussian behavior. It is remarkable that the stretching exponent $$beta$$ gradually changes in between the two crossover points. We consider that the two crossovers are the universal feature for glass-forming liquids.

論文

Neutron scattering studies on short- and long-range layer structures and related dynamics in imidazolium-based ionic liquids

根本 文也*; 古府 麻衣子; 長尾 道弘*; 大石 一城*; 高田 慎一; 鈴木 淳市*; 山田 武*; 柴田 薫; 上木 岳士*; 北沢 侑造*; et al.

Journal of Chemical Physics, 149(5), p.054502_1 - 054502_11, 2018/08

https://doi.org/10.1063/1.5037217
 被引用回数：24 パーセンタイル：74.13(Chemistry, Physical)

Alkyl-methyl-imidazolium ionic liquids C$$n$$mimX ($$n$$: alkyl-carbon number, X: anion) have short-range layer structures consisting of ionic and neutral (alkylchain) domains. To investigate the temperature dependences of the interlayer, interionic group, and inter-alkylchain correlations, we have measured the neutron diffraction (ND) of C$$n$$mimPF$$_6$$ ($$n$$ = 16, 9.5, 8). The quasielastic neutron scattering (QENS) of C16mimPF$$_6$$ was also measured to study the dynamics of each correlation. C16mimPF$$_6$$ shows a first-order transition between the liquid (L) and liquid crystalline (LC) phases at $$T_{rm c}$$ = 394 K. C8mimPF$$_6$$ exhibits a glass transition at $$T_{rm g}$$ = 200 K. C9.5mimPF$$_6$$ has both transitions at $$T_{rm c}$$ = 225 K and $$T_{rm g}$$ = 203 K. In the ND experiments, all samples exhibit three peaks corresponding to the correlations mentioned above. The widths of the interlayer peak at ca. 0.2 $AA$^{-1}$$ changed drastically at the L-LC transitions, while the interionic peaks at ca. 1 $AA$^{-1}$$ exhibited a small jump at $$T_{rm c}$$. The peak position and area of the three peaks did not change much at the transition. The structural changes were minimal at $$T_{rm g}$$. The QENS experiments demonstrated that the relaxation time of the interlayer motion increased tenfold at $$T_{rm c}$$, while those of other motions were monotonous in the whole temperature region. The structural and dynamical changes are characteristic of the L-LC transition in imidazolium-based ionic liquids.

論文

CIELO collaboration summary results; International evaluations of neutron reactions on uranium, plutonium, iron, oxygen and hydrogen

Chadwick, M. B.*; Capote, R.*; Trkov, A.*; Herman, M. W.*; Brown, D. A.*; Hale, G. M.*; Kahler, A. C.*; Talou, P.*; Plompen, A. J.*; Schillebeeckx, P.*; et al.

Nuclear Data Sheets, 148, p.189 - 213, 2018/02

https://doi.org/10.1016/j.nds.2018.02.003
 被引用回数：78 パーセンタイル：98.03(Physics, Nuclear)

CIELO国際協力では、原子力施設の臨界性に大きな影響を与える重要核種($$^{235}$$U, $$^{238}$$U, $$^{239}$$Pu, $$^{56}$$Fe, $$^{16}$$O, $$^{1}$$H)の中性子断面積データの精度を改善し、これまで矛盾していると考えられた点を解消することを目的として研究が行われた。多くの研究機関が参加したこのパイロットプロジェクトは、IAEAの支援も受けて、OECD/NEAの評価国際協力ワーキングパーティ(WPEC)のSubgroup 40として組織された。本CIELOプロジェクトは、新たな実験研究や理論研究を行う動機付けとなり、測定データを正確に反映し臨界性の積分テストに優れた新たな一連の評価済みライブラリとして結実した。本報告書は、これまでの研究成果と、本国際協力の次の段階の計画概要をまとめたものである。

論文

Neutron polarization analysis for biphasic solvent extraction systems

元川 竜平; 遠藤 仁*; 長尾 道弘*; Heller, W. T.*

Solvent Extraction and Ion Exchange, 34(5), p.399 - 406, 2016/07

https://doi.org/10.1080/07366299.2016.1201980
 被引用回数：5 パーセンタイル：17.92(Chemistry, Multidisciplinary)

We performed neutron polarization analysis (NPA) of extracted organic phases containing complexes, comprised of Zr(NO$$_{3}$$)$$_{4}$$ and tri-n-butyl phosphate (TBP), which enabled decomposition of the intensity distribution of small-angle neutron scattering (SANS) into the coherent and incoherent scattering components. The coherent scattering intensity, containing structural information, and the incoherent scattering compete over a wide range of magnitude of scattering vector, $$q$$, specifically when $$q$$ is larger than $$q$$ $$approx$$ 1/$$R_{rm g}$$, where $$R_{rm g}$$ is the radius of gyration of scatterer. Therefore, it is important to determine the incoherent scattering intensity exactly to perform an accurate structural analysis from SANS data when $$R_{rm g}$$ is small, such as the aforementioned extracted coordination species. Although NPA is the best method for evaluating the incoherent scattering component for accurately determining the coherent scattering in SANS, this method is not used frequently in SANS data analysis because it is technically challenging. In this study, we successfully demonstrated that experimental determination of the incoherent scattering using NPA is suitable for sample systems containing a small scatterer with a weak coherent scattering intensity, such as extracted complexes in biphasic solvent extraction system.

論文

Energy levels and spectral lines of tungsten, W III through W LXXIV

Kramida, A. E.*; 白井 稔三*

Atomic Data and Nuclear Data Tables, 95(3), p.305 - 474, 2009/05

https://doi.org/10.1016/j.adt.2008.12.002
 被引用回数：192 パーセンタイル：91.11(Physics, Atomic, Molecular & Chemical)

W$$^{2+}$$からW$$^{73+}$$までのエネルギー準位とスペクトル線を収集した。これらの実験データはW IIIからW VII, W XXVIIIからW LI, W LIII及びW LVからW LXVについて存在した。W VIIIの四つの最も低いエネルギー準位をW VIIのシリーズリミットより定めた。W LXIVとW LVIのエネルギー準位とスペクトル線の波長を等電子系列に沿って内挿及び外挿による予想値で補完した。W LXXIII及びW LXXIVのエネルギー準位とスペクトル線の波長については理論計算値を収録した。W IIIの自然放射確率については実験的に定められた値を収録した。基底状態の電子配置,項及び電離エネルギーをすべての電離段階について定めた。

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