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Saito, Takumi*; Motokawa, Ryuhei; Okubo, Takahiro*; Miura, Daisuke*; Kumada, Takayuki
Environmental Science & Technology, 57(26), p.9802 - 9810, 2023/07
Times Cited Count：0 Percentile：0(Engineering, Environmental)Shibata, Motoki*; Nakanishi, Yohei*; Abe, Jun*; Arima, Hiroshi*; Iwase, Hiroki*; Shibayama, Mitsuhiro*; Motokawa, Ryuhei; Kumada, Takayuki; Takata, Shinichi; Yamamoto, Katsuhiro*; et al.
Polymer Journal, 6 Pages, 2023/00
Times Cited Count：0 Percentile：0(Polymer Science)Kumada, Takayuki; Miura, Daisuke*; Akutsu, Kazuhiro*; Oku, Takayuki; Torikai, Naoya*; Niizeki, Tomotake*
Hamon, 32(4), p.165 - 168, 2022/11
We demonstrated the advantage of spin-contrast-variation neutron reflectometry on the structure analysis of buried interface between resin and porous silica layers. The interface structure was not reproduced by the normal Gaussian model, but by the asymmetric interface model where crosslinked polymer chains neither permeate the pore nor follow the surface roughness of the silica layer.
Kumada, Takayuki; Miura, Daisuke*; Akutsu, Kazuhiro*; Oishi, Kazuki*; Morikawa, Toshiaki*; Kawamura, Yukihiko*; Suzuki, Junichi*; Oku, Takayuki; Torikai, Naoya*; Niizeki, Tomotake*
Journal of Applied Crystallography, 55(5), p.1147 - 1153, 2022/10
Times Cited Count：1 Percentile：37.59(Chemistry, Multidisciplinary)Spin-contrast-variation neutron reflectivity obtains multiple reflectivity curves from a single sample and a single beam source. We used the strong point of the technique to reveal that, although methylated-perhydropolysilazane-derived silica layer has a higher porosity near the interface with acrylic urethane resin, the resin did not permeate the pore network.
Wada, Yoriko*; Akagi, Hiroshi*; Kumada, Takayuki; Itakura, Ryuji*; Wakabayashi, Tomonari*
Photochem (Internet), 2(3), p.798 - 809, 2022/09
Coulomb explosion experiments using 60 fs laser pulses were conducted for structural characterization of three dichloroethylene isomers. Under laser intensity at 1.8 
10
W/cm
, mass-resolved momentum imaging (MRMI) for selected fragment ions of 
Cl
and C
revealed different patterns for the three isomers. The C
ion fragmented from multiply charged trans-1,2-DCE was forced to leave perpendicularly to the direction of the laser polarization, due to recoil forces from adjacent cations. In contrast, the fast ions of C from cis-1,2-DCE exhibited an isotropic distribution, whereas the fast ions of C from 1,1-DCE recoiled along the laser polarization together with the slow C ions, and thereby distinction of the three isomers was demonstrated. Coulomb explosion occurs predominantly at specific orientation, which is useful for potential applications of MRMI analysis to molecular structure assays.
Miura, Daisuke*; Kumada, Takayuki; Sekine, Yurina; Oku, Takayuki; Takata, Shinichi; Hiroi, Kosuke; Iwata, Takahiro*
J-PARC 22-02; J-PARC MLF Annual Report 2021, p.6 - 7, 2022/03
We carried out spin contrast variation neutron powder diffractometry of glutamic acid crystal. The diffraction peak intensities varied as a function of proton polarization. We extracted the structure factor of hydrogen atoms from the variation of peak intensities.
Motokawa, Ryuhei; Kaneko, Koji; Oba, Yojiro; Nagai, Takayuki; Okamoto, Yoshihiro; Kobayashi, Taishi*; Kumada, Takayuki; Heller, W. T.*
Journal of Non-Crystalline Solids, 578, p.121352_1 - 121352_7, 2022/02
Times Cited Count：3 Percentile：26.93(Materials Science, Ceramics)Miura, Daisuke*; Kumada, Takayuki; Iwata, Takahiro*
Nihon Kessho Gakkai-Shi, 63(4), p.287 - 293, 2021/12
We have developed the spin-contrast-variation neutron powder diffractometry to observe hydrogen atoms in a crystalline sample by polarized neutron and polarized proton in the crystal. L-glutamic acid crystals were dispersed in a deuterated polystyrene matrix containing a polarizing agent. The intensities of the diffraction peaks of the sample changed according to the proton polarization. The spin-contrast-variation neutron powder diffractometry can extract diffraction from hydrogen atoms because of the variation of peak intensities as a function of the proton polarization. This technique is expected to enable analyses of the structures of hydrogen-containing materials that are difficult to determine with conventional powder diffractometry.
Miura, Daisuke*; Kumada, Takayuki; Sekine, Yurina; Motokawa, Ryuhei; Nakagawa, Hiroshi; Oba, Yojiro; Ohara, Takashi; Takata, Shinichi; Hiroi, Kosuke; Morikawa, Toshiaki*; et al.
Journal of Applied Crystallography, 54(2), p.454 - 460, 2021/04
Times Cited Count：1 Percentile：20.14(Chemistry, Multidisciplinary)We developed a spin-contrast-variation neutron powder diffractometry technique that extracts the structure factor of hydrogen atoms, namely, the contribution of hydrogen atoms to a crystal structure factor. Crystals of L-glutamic acid were dispersed in a dpolystyrene matrix containing 4-methacryloyloxy-2,2,6,6,-tetramethyl-1-piperidinyloxy (TEMPO methacrylate) to polarize their proton spins dynamically. The intensities of the diffraction peaks of the sample changed according to the proton polarization, and the structure factor of the hydrogen atoms was extracted from the proton-polarization dependent intensities. This technique is expected to enable analyses of the structures of hydrogen-containing materials that are difficult to determine with conventional powder diffractometry.
Kumada, Takayuki; Motokawa, Ryuhei; Nakagawa, Hiroshi; Oba, Yojiro; Sekine, Yurina
Hamon, 31(1), p.5 - 6, 2021/02
no abstracts in English
Kumada, Takayuki; Akutsu, Kazuhiro*; Oishi, Kazuki*; Morikawa, Toshiaki*; Kawamura, Yukihiko*; Sahara, Masae*; Suzuki, Junichi*; Miura, Daisuke*; Torikai, Naoya*
J-PARC 20-02; J-PARC MLF Annual Report 2019, p.38 - 40, 2021/00
Kumada, Takayuki; Miura, Daisuke*; Akutsu, Kazuhiro*; Suzuki, Junichi*; Torikai, Naoya*
Hamon, 30(4), p.207 - 211, 2020/11
We developed a technique of spin-contrast-variation neutron reflectivity (SCV-NR) for structural analyses of multilayer films. The SCV-NR curves of the polystyrene monolayer film were precisely reproduced using a common set of structural parameters and neutron scattering length density at each proton polarization. This result ensures that SCV-NR curves are not deformed by inhomogeneous PH due to the spin-diffusion mechanism. The number of structural parameters of the lamellar microphase-separated poly(styrene-block-isoprene) thin film is too large to determine with a single unpolarized reflectivity curve only. However, these parameters converged through the global analysis of the SCV-NR curves. In this manner, SCV-NR determines the structure of multilayer films while excluding the incorrect structural model that accidentally accounts for a single unpolarized reflectivity curve only.
Akagi, Hiroshi*; Kumada, Takayuki; Otobe, Tomohito*; Itakura, Ryuji*; Hasegawa, Hirokazu*; Oshima, Yasuhiro*
Chemistry Letters, 49(4), p.416 - 418, 2020/04
Times Cited Count：1 Percentile：5.45(Chemistry, Multidisciplinary)Kumada, Takayuki
Purazuma, Kaku Yugo Gakkai-Shi, 96(4), p.176 - 180, 2020/04
We have developed time-resolved reflectivity measurement system using femtosecond laser pulses, which can measure structure of thin films generated by non-thermal effect.
Kumada, Takayuki; Oba, Yojiro; Motokawa, Ryuhei; Morooka, Satoshi; Tominaga, Aki; Tanida, Hajime; Shobu, Takahisa; Konno, Azusa; Owada, Kenji*; Ono, Naoko*; et al.
Journal of Nuclear Materials, 528, p.151890_1 - 151890_7, 2020/01
Times Cited Count：1 Percentile：13.39(Materials Science, Multidisciplinary)We have developed an anomalous small-angle X-ray scattering (ASAXS) diffractometer in SPring-8 to investigate irradiation-induced nanostructural change in ion-beam irradiated stainless steel. A thermally-aged MA956 stainless steel sample displays power-law scattering that follows the Porod law at the magnitude of scattering vector, Q, below 0.5 nm
and an overlapped shoulder around 0.7 nm. After the ion-beam irradiation, the intensity of the shoulder remained unchanged, whereas that of the power-law scattering nearly doubled. This result indicates that none of the structural parameters of the Cr-rich nanoprecipitates, such as the number density, size, and interface roughness, were changed by the irradiation.
Kumada, Takayuki; Akutsu, Kazuhiro*; Oishi, Kazuki*; Morikawa, Toshiaki*; Kawamura, Yukihiko*; Sahara, Masae*; Suzuki, Junichi*; Torikai, Naoya*
Journal of Applied Crystallography, 52(5), p.1054 - 1060, 2019/10
Times Cited Count：3 Percentile：33.84(Chemistry, Multidisciplinary)We developed a technique of spin-contrast-variation neutron reflectometry (SCV-NR). Polarized-neutron reflectivity curves of film samples vary as a function of their proton-polarization P. The P-dependent reflectivity curves of a polystyrene film was precisely reproduced using a common set of structure parameters and the P-dependent neutron scattering length. The reflectivity curve of poly (styrene-block-isoprene) (PSPI) presented a shoulder attributed to holes with the depth corresponding to one period of periodic lamellae on the free surface only at a specific P. In this way, structural information about specific surfaces or interfaces can be obtained by controlling the P.
Kumada, Takayuki; 7 of others*
JPS Conference Proceedings (Internet), 22, p.011015_1 - 011015_5, 2018/11
Akagi, Hiroshi*; Kumada, Takayuki; Otobe, Tomohito*; Itakura, Ryuji*; Hasegawa, Hirokazu*; Oshima, Yasuhiro*
Applied Physics B, 124(1), p.14_1 - 14_8, 2018/01
Times Cited Count：2 Percentile：15.43(Optics)We propose and numerically simulate a method of laser isotope separation based on field-free alignment of isotopologues, utilizing an intense switched nanosecond (ns) laser field which is slowly turned on and rapidly turned off at the peak with the falling time of 200 fs. The femtosecond (fs) laser induced alignment of molecules including a heavy atom is severely disturbed by ionization because of their small ionization potential. Our simulations for I
Br and I
Br isotopologues demonstrate that the switched ns laser field can make isotopologues well-aligned with the reduced ionization probability at the laser intensity which is an order-of-magnitude lower than a typical intensity for field-free alignment induced by a fs laser field.
Kumada, Takayuki
Denshi Supin Saiensu, 15(Autumn), p.86 - 91, 2017/10
no abstracts in English
Kumada, Takayuki
Kagaku No Yoten Shirizu, 20, P. 71, 2017/06
no abstracts in English
