Papers - Chiba, Ayano

In Situ X-Ray and Infrared Measurements of Alkane Absorption and Desorption Processes of Isotactic Poly(4-Methyl-1-Pentene) Film

Hiromi Murashige, Yusuke Hiejima, Yusuke Sanada, Ayano Chiba

Macromolecular Symposia (Macromolecular Symposia)  408 ( 1 ) 2200090-1 - 2200090-5 2023.04

Research paper (scientific journal), Joint Work, Last author, Corresponding author, Accepted,  ISSN  10221360

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Small molecules are absorbed selectively in the amorphous regions in semicrystalline polymers, except for some specific polymeric systems forming host-guest cocrystals such as syndiotactic polystyrene. The crystalline density of isotactic poly(4-methyl-1-pentene) (P4MP1) is substantially lower than those of analogs, and it is even slightly lower than the amorphous density. This study is investigated the absorption/desorption behaviors of short alkanes in P4MP1 in situ, and found that the alkanes are mainly absorbed in its amorphous region. Infrared spectroscopy measurements reveal that the P4MP1 film with low crystallinity absorbs higher amount of decane than the high crystallinity film does. Also it is found by small-angle X-ray scattering (SAXS) that, when hexane is dropped onto the P4MP1 as-cast film, a lamellar long-spacing peak appears at 0.16 nm−1 which disappears with the spontaneous desorption of hexane. Because the pristine P4MP1 films give no obvious SAXS peak due to the close density of crystalline and amorphous regions, the appearance of the SAXS peak indicates that an X-ray contrast is obtained by the preferential absorption to amorphous region. The disappearance of the peak is thus reasonably understood by the loss of the contrast due to desorption.

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Low energy excitation in liquid Sb and liquid Bi observed in inelastic x-ray scattering spectra

Inui M., Kajihara Y., Hosokawa S., Chiba A., Nakajima Y., Matsuda K., Stellhorn J.R., Hagiya T., Ishikawa D., Uchiyama H., Tsutsui S., Baron A.Q.R.

Journal of Physics Condensed Matter (Journal of Physics Condensed Matter)  33 ( 47 )  2021.11

ISSN  09538984

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The dynamic structure factor S(Q, E), where Q and E are momentum and energy transfer, respectively, has been measured for liquid Sb, using inelastic x-ray scattering. A modified damped harmonic oscillator model function was applied to analyse S(Q, E) of liquid Sb and also to that of liquid Bi by Inui et al (2015 Phys. Rev. B 92, 054206). The obtained excitation energy was in fairly good agreement with that predicted by ab initio molecular dynamics simulations on these liquid semi-metals. The excitation energy of the longitudinal acoustic mode in liquid Sb and liquid Bi exhibits flat-topped Q dependence whereas the lower excitation energy below the longitudinal acoustic excitation shows Q-gap behaviour. From the viscosity estimated from the Q-gap experimentally obtained, it is inferred that the lower energy excitation arises from the transverse acoustic excitation in the liquids.

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Selective molecular absorption from low molecular weight mixed solution to a polymer p4mp1 film

Chiba A., Akiyama R.

Review of High Pressure Science and Technology/Koatsuryoku No Kagaku To Gijutsu (Review of High Pressure Science and Technology/Koatsuryoku No Kagaku To Gijutsu)  31 ( 2 ) 82 - 89 2021.10

Accepted,  ISSN  0917639X

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Recently isotactic poly(4-methyl-1-pentene) (P4MP1) has been found to selectively absorb long-chain alkanes from alkane mixed systems. In this article, we introduce the idea of this study from the pressure-temperature phase diagram. We also show that such selective absorption characteristics can be explained from a simple model, namely Asakura-Oosawa theory, and the relationship with molecular recognition is explained.

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Longitudinal acoustic and higher-energy excitations in the liquid phase-change material Ge2Sb2Te5

Inui M., Kajihara Y., Hosokawa S., Chiba A., Nakajima Y., Matsuda K., Tsuchiya Y., Stellhorn J.R., Hagiya T., Uchiyama H., Tsutsui S., Baron A.Q.R.

Physical Review B (Physical Review B)  104 ( 6 )  2021.08

ISSN  24699950

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The dynamic structure factor S(Q,E) of liquid Ge2Sb2Te5 has been obtained by inelastic x-ray scattering, where Q and E are momentum and energy transfer, respectively. The dispersion curve of the longitudinal acoustic excitation energy exhibits flat-topped Q dependence similarly to that in liquid GeTe and liquid Bi, where the local structure is modulated by Peierls distortion. The flat-topped energy in liquid Ge2Sb2Te5 is split into low and high energy parts arising from Sb-Te and Ge-Te correlations, respectively. Furthermore, the high energy part depends on Q like an optical mode with decreasing Q to zero, and it approaches the vibrational energy of fourfold coordinated Ge atoms with octahedral configurations. The result indicates that a majority of Ge in the liquid stays in octahedral order as predicted by first-principles molecular dynamics simulations.

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Streak Patterns Observed in Small Angle X-Ray Scattering from Highly Oriented Pyrolytic Graphite (HOPG)

Ohmasa Y., Chiba A.

Zeitschrift fur Physikalische Chemie (Zeitschrift fur Physikalische Chemie)  235 ( 1-2 ) 37 - 57 2020

ISSN  09429352

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© 2020 Walter de Gruyter GmbH, Berlin/Boston. Various forms of streak patterns are observed in small angle X-ray scattering from Highly Oriented Pyrolytic Graphite (HOPG). The streak patterns are assigned as specular reflection, double Bragg scattering, and diffuse + Bragg double scattering. These scatterings contain various information on the mesoscopic structures of the HOPG sample.

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Confined Space Enables Spontaneous Liquid Separation by Molecular Size: Selective Absorption of Alkanes into a Polyolefin Cast Film

Ayano Chiba, Akio Oshima,and Ryo Akiyama

Langmuir (ACS Publications)  35 ( 52 ) 17177 - 17184 2019.11

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0743-7463

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© 2019 American Chemical Society. The depletion force has been used to explain phase separation phenomena in colloidal systems. Here, we showed that depletion force can explain not only phase separation of large and small colloidal particles but also preferential absorption of larger molecules from a mixture of large and small molecules in a liquid state. When a polyolefin cast film was immersed in a mixture of long and short normal alkanes, the longer molecules were selectively absorbed into the film. This experimental result was explained from the viewpoint of depletion force. The main finding was the use of confined space to emphasize the separation tendency caused by the force. In general, the increase in entropy may serve as a driving force to mix molecules. However, if sufficiently narrow pores are present, large and small molecules are separated naturally by size as the entropy increases. This finding will lead to size exclusion chromatography of low-mass molecules, similar to gel permeation chromatography of macromolecules. In order to demonstrate the effect of depletion force, we selected and experimented with a system based on a polyolefin isotactic poly(4-methyl-1-pentene) (P4MP1) film and a normal alkane mixture and realized high molecular selectivity. The P4MP1 film we used can be prepared simply by evaporating the solvent from the solution and casting the film. On the basis of the Asakura-Oosawa theory, we concluded that spontaneous and high molecular selectivity is attributed to the depletion force provided by the small sub-nanopores with uniform size in the film.

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Structural studies on fluid sulfur at high temperatures and high pressures: I. Atomic dynamics investigated by inelastic x-ray scattering

Inui M., Kajihara Y., Chiba A., Matsuda K., Tsutsui S., Baron A.

Journal of Non-Crystalline Solids (Journal of Non-Crystalline Solids)  522 2019.10

ISSN  00223093

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© 2019 Elsevier B.V. Inelastic x-ray scattering spectra of fluid S were measured from 403 K near the melting point to 1343 K in the supercritical region at 25 MPa. Although the dynamic structure factor in the supercritical region exhibits a single peak profile, the spectrum includes collective inelastic excitations besides the quasielastic component. The acoustic excitation energy in the supercritical region is close to the one predicted by the sound speed in the fluid consisting of S8 molecules and the observed excitation energies of the stretching modes in S molecules suggest that few fraction of S2 molecules in the supercritical region near the liquid-vapor critical point. This result indicates that the nearest neighbor coordination number in the supercritical fluid S obtained by x-ray diffraction [Inui et al., J. Phys. Conf. Ser. 98 (2008) 012008] was underestimated.

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Diffuse + Bragg double scattering and specular reflection observed in the small-angle X-ray scattering from highly oriented pyrolytic graphite

Y. Ohmasa, A. Chiba

Journal of Applied Crystallography (International Union of Crystallography (IUCr))  52 ( 3 ) 652 - 664 2019.06

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1600-5767

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© International Union of Crystallography, 2019 In the small-angle scattering from as-prepared and neutron-irradiated highly oriented pyrolytic graphite samples, a new type of streak pattern is observed near the -type double Bragg scattering. This newly observed scattering is assigned as the double scattering whose first scattering is diffuse scattering near the 00l Bragg scattering and whose second scattering is the Bragg scattering. Specular reflection from the surfaces of the crystallites or microcracks is also observed as a streak. These two types of scattering from the neutron-irradiated sample show oscillatory behavior, unlike that from the non-irradiated samples. The scattering is analyzed using the sharp-boundary model, and is explained by the assumptions that the non-irradiated sample has interfaces with a width of about 1 nm and the neutron-irradiated sample has a slab-like structure with a thickness of about 14 nm.

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Intensity distribution profile of double Bragg scattering in the small-angle region from highly oriented pyrolytic graphite

Yoshinori Ohmasa and Ayano Chiba

Acta Crystallographica Section A (International Union of Crystallography (IUCr))  74 ( 6 ) 681 - 698 2018.10

Research paper (scientific journal), Joint Work, Accepted,  ISSN  2053-2733

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© International Union of Crystallography, 2018 It is observed that radial streak patterns of double Bragg scattering appear in the small-angle X-ray scattering from highly oriented pyrolytic graphite (HOPG). The intensity profile of double Bragg scattering from an HOPG sample is calculated theoretically. Assuming that the c axes of the graphite crystallites in the HOPG sample are distributed around an orientation vector and their distribution function has a Gaussian form, it is found that the intensity profile of double Bragg scattering is expressed by a double Gaussian function of the scattering angle and the azimuthal angle of the streak. The calculated intensity profile is compared with the experimental one. The method developed in this article can be used to estimate the orientational distribution of crystallites in uniaxial polycrystalline materials.

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Peculiar atomic dynamics in liquid GeTe with asymmetrical bonding: Observation by inelastic x-ray scattering

M. Inui, A. Koura, Y. Kajihara, S. Hosokawa, A. Chiba, K. Kimura, F. Shimojo, S. Tsutsui, and A. Q. R. Baron

Physical Review B (American Physical Society)  97 ( 17 ) 174203-1 - 174203-10 2018.05

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1098-0121

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© 2018 American Physical Society. Collective dynamics in liquid GeTe was investigated by inelastic x-ray scattering at 2≤Q≤31nm-1. The dynamic structure factor shows clear inelastic excitations. The excitation energies at low Q disperse with increasing Q, consistent with the behavior of a longitudinal-acoustic excitation. The dispersion curve has a flat-topped region around the pseudo-Brillouin-zone boundary, similar to what is observed in liquid Bi [Inui, Phys. Rev. B 92, 054206 (2015)PRBMDO1098-012110.1103/PhysRevB.92.054206]. The dynamic structure factor shows a low-frequency excitation, and its coupling with the longitudinal-acoustic mode plays an important role for a flat-topped dispersion. From these results, it is inferred that atomic dynamics in liquid GeTe is strongly affected by a Peierls distortion similar to liquid Bi. By comparing the momentum transfer dependence of the excitation energy and quasielastic linewidth to partial structure factors obtained by our own ab initio molecular dynamics simulation for liquid GeTe, the quasielastic and inelastic components were found to be correlated with Te-Te and Ge-(Ge,Te) partial structure factors, respectively.

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X-ray Compton Scattering Study of Liquid Germanium and Tin

Koji Kimura, Kazuhiro Matsuda, Takena Nagao, Toru Hagiya, Yukio Kajihara, Masanori Inui, Jumpei Nakamura, Ayano Chiba, Kouichi Hayashi, Masayoshi Itou, and Yoshiharu Sakurai

Journal of Physical Society of Japan (Physical Society of Japan)  86   124703-1 - 124703-6 2017.11

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1347-4073

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Asymmetrical bonding in liquid Bi disentangled by inelastic X-ray scattering

Masanori Inui1, Yukio Kajihara, Shuji Munejiri, Shinya Hosokawa, Ayano Chiba, Koji Ohara, Satoshi Tsutsui and Alfred Q. R. Baron

EPJ Web of Conferences (Società Italiana di Fisica and Springer-Verlag)  151   06001-1 - 06001-7 2017.08

Research paper (international conference proceedings), Joint Work, Accepted,  ISSN  1434-6052

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Dispersion relations of the acoustic modes in divalent liquid metals

Masanori Inui, Yukio Kajihara, Koji Kimura, Kazuhiro Matsuda, Tetsu Miyatake, Ayano Chiba, Shinya Hosokawa, Satoshi Tsutsui, and Alfred Q. R. Baron

EPJ Web of Conferences (Società Italiana di Fisica and Springer-Verlag)  151   06002-1 - 06002-6 2017.08

Research paper (international conference proceedings), Joint Work, Accepted,  ISSN  1434-6052

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Isotactic poly(4-methyl-1-pentene) melt as a porous liquid: Reduction of compressibility due to penetration of pressure medium

Ayano Chiba, Masanori Inui, Yukio Kajihara, Kazuhiro Fuchizaki, Ryo Akiyama

The Journal of Chemical Physics (American Institute of Physics)  146 ( 19 ) 194503-1 - 194503-5 2017.05

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1089-7690

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Phonon Excitations in Pd40Ni40P20 Bulk Metallic Glass by Inelastic X-Ray Scattering

Shinya Hosokawa, Masanori Inui, Yukio Kajihara, Tetsu Ichitsubo, Kazuhiro Matsuda, Hidemi Kato, Ayano Chiba, Koji Kimura, Kenji Kamimura, Satoshi Tsutsui, Hiroshi Uchiyama, Alfred Q R Baron

Materials Science Forum (Trans Tech Publications, Swizerland)  879   767 - 772 2016.11

Research paper (international conference proceedings), Joint Work, Accepted

Double Bragg scattering observed in small-angle X-ray scattering from highly oriented pyrolytic graphite

Yoshinori Ohmasa, Susumu Shimomura, Ayano Chiba

Journal of Applied Crystallography (IUCr)  49 ( 3 ) 835 - 844 2016.06

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1600-5767

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構造不規則系の中距離秩序：空隙と圧力依存性

CHIBA AYANO, TAKENAKA MIKIHITO

Journal of the Crystallographic Society of Japan (The Crystallographic Society of Japan)  58 ( 1 ) 48 - 52 2016.03

Research paper (scientific journal), Accepted,  ISSN  0369-4585

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Anomalous dispersion of the acoustic mode in liquid Bi

M. Inui, Y. Kajihara, S. Munejiri, S. Hosokawa, A. Chiba, K. Ohara, S. Tsutsui, A. Q. R. Baron

Physical Review B 92   054206-1 - 054206-8 2015.08

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1098-0121

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Structural Changes of Short- and Intermediate-Range Order in Liquid Arsenic under Pressure

Satoshi Ohmura, Ayano Chiba, Yasuyuki Yanagawa, Akihide Koura, Kazuhiko Tsuji, and Fuyuki Shimojo

Journal of Physical Society of Japan 84   094602-1 - 094602-6 2015.08

Joint Work, Accepted,  ISSN  1347-4073

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Structurally different amorphous solids of isotactic poly(4-methyl-1-pentene) and an apparently press-working-induced amorphization

CHIBA AYANO

Journal of Molecular Liquids (Elsevier B. V.)  200   28 - 31 2014.12

Research paper (scientific journal), Single Work, Accepted,  ISSN  0167-7322

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Pressure-induced structural change of intermediate-range order in a polymer melt

Ayano Chiba, Nobumasa Funamori, Mikihito Takenaka

SPring-8 Research Frontiers 2012    82-83 2013.08

Research paper (bulletin of university, research institution), Joint Work, Accepted,  ISSN  1349-0087

液体・液体構造相転移：リン，水から高分子まで

CHIBA AYANO

固体物理 48 ( 3 ) 1-11 2013.03

Research paper (scientific journal), Single Work, Accepted

二つの顔をもつ溶融高分子 --- 圧力に応じて異なる構造をとっていた！

CHIBA AYANO

化学　２０１２年７月号 67 ( 7 ) 25-28 2012.07

Research paper (scientific journal), Single Work

Pressure-induced structural change of intermediate-range order in poly(4-methyl-1-pentene) melt

Ayano Chiba, Nobumasa Funamori, Kazuya Nakayama, Yasuo Ohishi, Stephen M. Bennington, Sanjay Rastogi, Anuj Shukla, Kazuhiko Tsuji, Mikihito Takenaka

Physical Review E 85 ( 2 ) 021807-1-5 2012.02

Research paper (scientific journal), Joint Work, Accepted

10560442262820120228072915PDF1.pdf

The structure of liquid SnTe under pressure

Andreas Hinzmann, Ayano Chiba*, Kazuhiko Tsuji

J. Phys.: Condens. Matter 24   115103-1-5 2012.02

Research paper (scientific journal), Joint Work, Accepted

Pressure-Induced Structural Changes in Liquid Ge33Te67 and Liquid Ge15Te85

Jumpei Nakamura, Ayano Chiba, Kazuhiko Tsuji

Journal of Physical Society of Japan 79 ( 6 ) 064604-1-4 2010.05

Research paper (scientific journal), Joint Work, Accepted

Pressure dependence of hopping conduction in amorphous Ge alloys

Mariko Sugisaki , Ayano Chiba and Kazuhiko Tsuji

Journal of Physics: Conference Series 215   012082 2010.03

Research paper (scientific journal), Joint Work, Accepted

Pressure-induced structural change in liquid Ge0.15Te0.85 alloy

T Tsukatani, A Chiba and K Tsuji

Journal of Physics: Conference Series 215   012076 2010.03

Research paper (scientific journal), Joint Work, Accepted

Relationship between Peierls Distortion and Medium-Range Order in Liquid Group-V elements and Liquid Group-IV-VI Compounds

A Chiba, M Tomomasa, T Hayakawa, A Hinzmann, R Takahashi, J Nakamura, T Tsukatani, T Kumazawa, K Tsuji

Journal of Physics: Conference Series 215   012077-1-5 2010.03

Research paper (scientific journal), Joint Work, Accepted

10560437940520100506151707PDF1.pdf

領域6,領域12「液体系の物理の最新の展開-中・長距離領域の秩序を焦点に」

CHIBA AYANO, Masatoshi Ichikawa

日本物理学会誌 65 ( 2 ) 115 2010.02

Research paper (other academic), Joint Work

10560442287620120305191216PDF1.pdf

Pressure-induced suppression of the Peierls distortion of liquid As and GeX (X=S,Se,Te)

Ayano Chiba, Masatoshi Tomomasa, Takazumi Hayakawa, Stephen M. Bennington, Alex C. Hannon, and Kazuhiko Tsuji

Physical Review B 80 ( 6 ) 060201(R) 2009.08

Research paper (scientific journal), Joint Work, Accepted

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The terminology “Peierls distortion (PD)” has been widely accepted in disordered systems ever since the discovery of PD in liquid As [R. Bellissent et al., Phys. Rev. Lett. 59, 661 (1987)]. It has not been clarified, however, to what extent the PD in liquids mirrors the PD in crystals. Here we report the observation on the pressure-induced suppression of PD in liquid As and liquid GeX (X=S,Se,Te), by which we clarified the qualitative differences as well as similarities between the PD of liquid and crystalline systems. By the appearance of prepeak that accompanies PD, we show that the intermediate-range order is related to the “Peierls distortion” in liquids, just as the Peierls distortion doubles the periodicity in one-dimensional lattice model.

液体ヒ素およびIV-VI化合物の圧力誘起構造変化

CHIBA AYANO

高圧力の科学と技術 18 ( 4 ) 335-342 2008.12

Research paper (scientific journal), Joint Work, Accepted

The structure of liquid Sb under pressure

Ayano Chiba, Masatoshi Tomomasa, Takuya Higaki, Takazumi Hayakawa, Ryota Takahashi, Kazuhiko Tsuji

J. Phys.: Conf. Ser. 121   022019-1-4 2008.07

Research paper (scientific journal), Joint Work, Accepted

Pressure-induced structural change in liquid GeTe and liquid GeSe

M Tomomasa, T Higaki, T Hayakawa, A Chiba, K Tsuji

J. Phys.: Conf. Ser. 121   022007-1-5 2008.07

Research paper (scientific journal), Single Work, Accepted

Analysis of the optic-type collective mode in liquid selenium to determine the local structure

Ayano Chiba, Yoshinori Ohmasa, Stephen M. Bennington, Jon W. Taylor, Makoto Yao

Phys. Rev. B 77 ( 13 ) 132202-1-4 2008.04

Research paper (scientific journal), Joint Work, Accepted

Pressure dependence of the structure of liquid copper halides

Takuya Higaki, Masatoshi Tomomasa, Takazumi Hayakawa, Ayano Chiba and Kazuhiko Tsuji

J. Phys.: Condens. Matter 20 ( 11 ) 114106-1-5 2008.03

Research paper (scientific journal), Joint Work, Accepted

Pressure dependence of the structure of liquid copper halides

Takuya Higaki, Masatoshi Tomomasa, Takazumi Hayakawa, Ayano Chiba and Kazuhiko Tsuji

Journal of Physics: Conference Series 98 ( 1 ) 012001-1-8 2008

Research paper (scientific journal), Joint Work, Accepted

Pressure and temperature dependence of the structure of liquid arsenic and antimony

Ayano Chiba, Masatoshi Tomomasa, Takuya Higaki, Takazumi Hayakawa and Kazuhiko Tsuji

J. Phys.: Conf. Ser. 98 ( 1 ) 012011-1-4 2008

Research paper (scientific journal), Joint Work, Accepted

Highly Oriented Nanowires From the Hierarchical Self-Assembly in Supramolecular Complex of Polyaniline with w-Methoxy Poly(ethylene oxide) Phosphates

B. Nandan, J.-Y. Hsu, A. Chiba, H.-L. Chen, C.-S. Liao, S.-An Chen, H. Hasegawa

Macromolecules 40 ( 3 ) 395 2007.03

Research paper (scientific journal), Single Work, Accepted

Inter- and Intra-molecular dynamics in liquid Se2Br2

Yukinobu Kawakita, Ayano Chiba, Yukinobu Yokota, Makoto Yao, Kaoru Shibata, Yoshinori Ohmasa, Shin'ichi Takeda

Physica B 385-386   256-258 2006.11

Research paper (scientific journal), Joint Work, Accepted

Time-resolved small-angle x-ray scattering studies on the formation of Bacteria Cellulose

Ayano Chiba, Mikihito Takenaka, Yasuyuki Takahashi, Takeji Hashimoto

物性研究 (Bussei Kenkyu) 84 ( 6 ) 979-980 2005.09

Research paper (conference, symposium, etc.), Single Work

Dynamic structure of liquid chalcogens in the semiconductor-to-metal transition range

CHIBA AYANO, Makoto Yao, Yoshinori Ohmasa, Yusuke Hiejima, Yukinobu Kawakita, Stephen M. Bennington

Journal of Neutron Research 13 ( 1-3 ) 149-152 2005.03

Research paper (scientific journal), Joint Work, Accepted

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Dynamic structures of liquid Te 70 Se 30 and Te 50 Se 50 were investigated by inelastic neutron scattering experiments in the semiconductor-to-metal transition range. The bond-stretching modes for the both liquid mixtures were found to clearly soften when the transition occurs. We discuss the change of static and dynamic structures that accompany the transition.

X-ray Absorption and De-Excitation Processes of Krypton Clusters Studied by the XAFS-PEPICO Synchronous Measurements

K. Nagaya, A. Mori, H. Murakami, M. Yao, Y. Ohmasa, H. Kajikawa, K. Kobayashi, Y. Kajihara, A. Chiba, Y. Nishikawa, M. Ishii, Y. Fujii, E. Hayata

Physica Scripta T115   984 2005

Research paper (scientific journal), Joint Work, Accepted

パラジウムナノ微粒子の生成過程のその場観察

千葉 文野, Sivaniah Easan, 橋本 竹治

物性研究 83 ( 3 ) 329-330 2004.12

Research paper (scientific journal), Joint Work

Optic-type vibrational modes of liquid chalcoens

CHIBA AYANO, Yoshinori Ohmasa, Makoto Yao, Stephen M. Bennington

Journal of neutron research 12 ( 4 ) 301-304 2004.12

Research paper (scientific journal), Joint Work, Accepted

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We carried out inelastic neutron scattering measurements to study the dynamic structure of liquid Se and Te50Se50. The bond-stretching modes for both liquids were found to lie in higher energies than those forming a trigonal phase, showing that the chainlike molecules are more isolated than in the troigonal phase. The Q-dependence of the intensity of the dynamic structure factor was examined at the region of the stretching modes, and found to be explained by a simple model where we assumed completely out-of-phase motions of two atoms. The result shows the possibilities of extracting short-range structural information from such Q-dependences for these kinds of basically isolated molecules.

Dynamic structure of liquid Se, Te and Se-Te mixtures by neutron scattering measurements

CHIBA AYANO, Makoto Yao, Yoshinori Ohmasa, Jon Taylor, Stephen M. Bennington

AIP Conference Proceedings 708   436 2004.09

Research paper (scientific journal), Joint Work, Accepted

Vibrational, single-particle-like, and diffusive dynamics in liquid Se, Te, and Te50Se50

CHIBA AYANO, Yoshinori Ohmasa, and Makoto Yao

Journal of Chemical Physics 119 ( 17 ) 9047-9062 2003.11

Research paper (scientific journal), Joint Work, Accepted

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Neutron scattering measurements were carried out for liquid Se, liquid Te, and liquid Te50Se50. The results are discussed in the context of semiconductor-to-metal transition. As to liquid Te50Se50, the vibrational modes show a remarkable change when the semiconductor-to-metal transition occurs by temperature increase. A soft stretching mode was observed for the metallic phase and it shows the structural change; the appearance of long bonds in the metallic phase. The vibrational modes for liquid Se and liquid Te were obtained and agreed well with former works. The crossover from collective to single-particle-like regime was also observed for all liquid samples and the transition ranges (Q = 4.5–8 Å–1) are presented. The diffusive features in the low-Q region and single-particle-like properties in the high-Q region are discussed and are shown to be consistent with the results for the vibrational modes.

Neutron scattering studies of liquid tellurium–selenium mixtures

CHIBA AYANO, Yoshinori Ohmasaa, Yukinobu Kawakita, Makoto Yao and Hirohisa Endo

Journal of Non-Crystalline Solids 312-314   384-387 2002.10

Research paper (scientific journal), Joint Work, Accepted

Quasielastic Neutron Scattering of Liquid Te50Se50 in the Semiconductor-to-Metal Transition Range

CHIBA AYANO, Yoshinori Ohmasa, Makoto Yao, Oleg Petrenko and Yukinobu Kawakita

Journal of the Physical Society of Japan 71 ( 2 ) 504-509 2002.02

Research paper (scientific journal), Joint Work, Accepted

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We have carried out neutron scattering experiments for liquid Te50Se50 at 700 K (semiconducting regime), 900 K (transition regime) and 1100 K (metallic regime). The quasielastic scattering peak is comparatively narrow at the peak positions of S(Q). A remarkable increase in the peak width is observed near the first minimum of S(Q), when the semiconductor-to-metal transition occurs. Since the first peak of S(Q) in this system proves to mainly reflect the inter-chain correlation and the second peak to the intra-chain correlation, the observed broadening may suggest frequent bond-switching between the chains in the metallic regime.

Neutron Inelastic Scattering Measurements of Liquid Se2X2 (X: Halogen)

CHIBA AYANO, YUKINOBU KAWAKITA, YOSHINORI OHMASA, YUSUKE HIEJIMA, MAKOTO YAO

Analytical Sciences 17   i1089-i1092 2001

Research paper (scientific journal), Joint Work, Accepted

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We measured the vibrational spectra of liquid Se2Cl2 and Se2Br2 by neutron and Raman scattering. The spectra measured by each technique show roughly good agreements with earlier Raman works. A partial disagreement was observed for the neutron scattering data at the bond-bending mode of liquid Se2Br2. It is suggested that the disagreement might be attributed to the slightly dispersive behaviour of the mode. The generalized vibrational density of states, G(Q,E), for Se2Br2 obtained by neutron scatterings is reported to show the observed vibrational modes in the energy-momentum space.