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Journal Articles

Anomalous behavior of liquid molecules near solid nanoparticles; Novel interpretation on thermal conductivity enhancement in nanofluids

Hashimoto, Shunsuke*; Yamaguchi, Satoshi*; Harada, Masashi*; Nakajima, Kenji; Kikuchi, Tatsuya*; Oishi, Kazuki*

Journal of Colloid and Interface Science, 638, p.475 - 486, 2023/05

https://doi.org/10.1016/j.jcis.2023.01.101

Times Cited Count：2 Percentile：66.51(Chemistry, Physical)

Recently, it has been reported that anomalous improvement in the thermal conductivity of nanofluid composed of base liquids and dispersed solid nanoparticles, compared to the theoretically predicted value calculated from the particle fraction. Generally, the thermal conductivity values of gases and liquids are dominated by the mean free path of the molecules during translational motion. Herein, we present solid evidence showing the possible contribution of the vibrational behavior of liquid molecules around nanoparticles to increasing these thermal conductivities.

Journal Articles

Dynamics of radiocaesium within forests in Fukushima; Results and analysis of a model inter-comparison

Hashimoto, Shoji*; Tanaka, Taku*; Komatsu, Masabumi*; Gonze, M.-A.*; Sakashita, Wataru*; Kurikami, Hiroshi; Nishina, Kazuya*; Ota, Masakazu; Ohashi, Shinta*; Calmon, P.*; et al.

Journal of Environmental Radioactivity, 238-239, p.106721_1 - 106721_10, 2021/11

https://doi.org/10.1016/j.jenvrad.2021.106721

Times Cited Count：11 Percentile：56.59(Environmental Sciences)

This study was aimed at analysing performance of models for radiocesium migration mainly in evergreen coniferous forest in Fukushima, by inter-comparison between models of several research teams. The exercise included two scenarios of countermeasures against the contamination, namely removal of soil surface litter and forest renewal, and a specific konara oak forest scenario in addition to the evergreen forest scenario. All the models reproduced trend of time evolution of radiocesium inventories and concentrations in each of the components in forest such as leaf and organic soil layer. However, the variations between models enlarged in long-term predictions over 50 years after the fallout, meaning continuous field monitoring and model verification/validation is necessary.

JAEA Reports

Theoretical study of the Cs isotope exchange reaction of CsI + Cs' Cs + ICs' (Contract research)

Kobayashi, Takanori; Hashimoto, Masashi; Yokoyama, Keiichi

JAEA-Research 2015-014, 7 Pages, 2015/12

JAEA-Research-2015-014.pdf:2.46MB

To discuss the exchange reaction of Cs isotope by CsI + Cs' Cs + ICs', the structure and chemical properties of CsI intermediate and potential energy surface are calculated using M06/def2-TZVPPD density functional calculation. The calculation shows that the reaction to the intermediate has no barrier and the two Cs-I bonds of CsI are chemically equivalent. Thus, the collision of CsI + Cs' results in Cs exchange with the high probability.

Journal Articles

Theoretical study for laser isotope separation of heavy-element molecules in a thermal distribution

Matsuoka, Leo; Ichihara, Akira; Hashimoto, Masashi; Yokoyama, Keiichi

Proceedings of International Conference on Toward and Over the Fukushima Daiichi Accident (GLOBAL 2011) (CD-ROM), 7 Pages, 2011/12

Journal Articles

Numerical study on quantum walks implemented on the cascade rotational transitions in a diatomic molecule

Matsuoka, Leo; Kasajima, Tatsuya; Hashimoto, Masashi; Yokoyama, Keiichi

Journal of the Korean Physical Society, 59(4), p.2897 - 2900, 2011/10

https://doi.org/10.3938/jkps.59.2897

Times Cited Count：13 Percentile：62.2(Physics, Multidisciplinary)

Journal Articles

Oxygen isotope separation utilizing two-frequency infrared multiphoton dissociation of 2,3-dihydropyran

Hashimoto, Masashi; Oba, Hironori; Yokoyama, Atsushi

Applied Physics B, 104(4), p.969 - 974, 2011/09

https://doi.org/10.1007/s00340-011-4630-0

Times Cited Count：1 Percentile：7.18(Optics)

Oxygen isotope separation has been examined by utilizing the two-frequency infrared multiphoton dissociation (IRMPD) of 2,3-dihydropyran (DHP). The two-frequency IRMPD reduces remarkably the required laser fluence. For example, dissociation probability of DHP containing $^{18}$ O (D( $^{18}$ O)) and enrichment factor (S) were obtained to be 1.610 $^{-3}$ /pulse and 316 respectively by the simultaneous irradiation with 1052.2 cm $^{-1}$ photons at 0.45 J/cm $^{2}$ and 1031.5 cm $^{-1}$ photons at 1.06 J/cm $^{2}$ . These are comparable with D( $^{18}$ O) = 2.210 $^{-3}$ /pulse and S = 391 obtained by the single-frequency irradiation of 1033.5 cm $^{-1}$ photons at 2.2 J/cm $^{2}$ . Therefore, the production rate of an $^{18}$ O enriched dissociation product has been increased to four times or more, compared with the single-frequency IRMPD, and this two-frequency method would promise a practical large scale separation.

Journal Articles

Isotope production for medical usage using fast neutron reactions

Hatsukawa, Yuichi; Nagai, Yasuki; Kin, Tadahiro; Segawa, Mariko; Harada, Hideo; Iwamoto, Osamu; Iwamoto, Nobuyuki; Ochiai, Kentaro; Takakura, Kosuke; Konno, Chikara; et al.

Proceedings in Radiochemistry, 1(1), p.327 - 329, 2011/09

https://www.degruyter.com/downloadpdf/j/rcpr.2011.1.issue-1/rcpr.2011.0057/rcpr.2011.0057.pdf

Authors proposed a new route to produce $^{99}$ Mo by the $^{100}$ Mo(,2) $^{99}$ Mo reaction, which has some characteristic features. Such as the reaction cross section is large, about 1.5 barn at 12 $_{rm n}$ 17 MeV, which is 10 times larger than the thermal-neutron capture cross section of $^{98}$ Mo. Second, the cross sections of the (,), (,), and (,) reactions are less than a few mb at $_{rm n}$ = 14 MeV. Third, a large amount of $^{100}$ Mo target materials can be used, compared to that for proton beam irradiation on $^{100}$ Mo. Fourth, intense neutrons with energy of 12-17 MeV are already available. In the present work we have measured all -rays emitted from activities produced by bombarding a natural Mo target with neutrons from the D(H,)He reaction at Fusion Neutronics Source Facility (FNS) at Japan Atomic Energy Agency (JAEA) to study characteristic features mentioned above more in detail. The neutron flux was about 10 $^{12}$ n/cms. The experimental results at FNS will be discussed in the conference.

Journal Articles

Narrow-band regenerative amplifier for momentum imaging spectroscopy of molecules

Matsuoka, Leo; Hashimoto, Masashi; Yokoyama, Keiichi

Proceedings of International Quantum Electronics Conference and the Pacific Rim Conference on Lasers and Electro-Optics (IQEC/CLEO Pacific Rim 2011) (CD-ROM), p.1363 - 1364, 2011/08

http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=6193760

Journal Articles

Numerical study on quantum walks implemented on the cascade rotational transitions in a diatomic molecule

Matsuoka, Leo; Kasajima, Tatsuya; Hashimoto, Masashi; Yokoyama, Keiichi

arXiv.org (Internet), 5 Pages, 2011/04

http://arxiv.org/abs/1104.4157

Journal Articles

Practical method for producing a large amount of isotopically enriched silicon by infrared multi-photon dissociation of hexafluorodisilane

Oba, Hironori; Akagi, Hiroshi; Katsumata, Keiichi*; Hashimoto, Masashi; Yokoyama, Atsushi

Japanese Journal of Applied Physics, 47(11), p.8379 - 8381, 2008/11

https://doi.org/10.1143/JJAP.47.8379

Times Cited Count：4 Percentile：18.78(Physics, Applied)

This paper presents a practical method for producing highly enriched silicon isotopes utilizing laser irradiation. One- or two-frequency CO $_{2}$ laser irradiation has been employed to separate the desired isotope of silicon by means of infrared multi-photon dissociation (IRMPD) of the hexafluorodisilane (Si $_{2}$ F $_{6}$ ) molecules using a flow reaction system. The production of Si $_{2}$ F $_{6}$ with $^{28}$ Si fraction of 99.1% at a rate of 0.67 g( $^{28}$ Si)/h was successfully accomplished with a high yield by the two-frequency laser irradiation. The enriched SiF $_{4}$ gas with $^{30}$ Si exceeding 31% was also continuously obtained at the production rate of 0.12 g/h by the one-frequency laser irradiation.

Journal Articles

Silicon isotope separation utilizing infrared multiphoton dissociation of Si $_{2}$ F $_{6}$ irradiated with two-frequency CO $_{2}$ laser lights

Yokoyama, Atsushi; Oba, Hironori; Hashimoto, Masashi; Katsumata, Keiichi; Akagi, Hiroshi; Ishii, Takeshi*; Oya, Akio*; Arai, Shigeyoshi*

Applied Physics B, 79(7), p.883 - 889, 2004/11

https://doi.org/10.1007/s00340-004-1642-z

Times Cited Count：9 Percentile：42.05(Optics)

Silicon isotope separation has been done utilizing the Infrared Multiphoton Dissociation of Si $_{2}$ F $_{6}$ irradiated with two-frequency CO $_{2}$ laser lights. The two-frequency excitation method improved the separation efficiency with keeping the high enrichment factors. For example, Si $_{2}$ F $_{6}$ with the $^{28}$ Si fraction of 99.4 % was obtained at 40.0 % dissociation of Si $_{2}$ F $_{6}$ after the simultaneous irradiation of 100 pulses with 966.23 cm $^{-1}$ photons (0.089 J/cm $^{2}$ ) and 954.55 cm $^{-1}$ photons (0.92 J/cm $^{2}$ ), while 1000 pulses were needed to obtain 99.0 % of $^{28}$ Si at 27.2 % dissociation in the case of single frequency irradiation at 954.55 cm $^{-1}$ (0.92 J/cm $^{2}$ ). The single-step enrichment factors of $^{29}$ Si and $^{30}$ Si increased with increasing Si $_{2}$ F $_{6}$ pressure. The reason for this enhancement has been discussed in terms of the rotational and vibrational relaxations by collisions with ambient gases.

Journal Articles

Production of hyperlithiated Li $_{2}$ F by a laser albation of LiF-Li $_{3}$ N mixture

Yokoyama, Keiichi; Haketa, Naoki*; Hashimoto, Masashi; Furukawa, Katsutoshi; Tanaka, Hiromasa*; Kudo, Hiroshi*

Chemical Physics Letters, 320(5-6), p.645 - 650, 2000/04

https://doi.org/10.1016/S0009-2614(00)00260-8

Times Cited Count：36 Percentile：72.25(Chemistry, Physical)

no abstracts in English

Journal Articles

He accumulation effect in solid and liquid D-T mixture

*; Nagamine, Kanetada*; Matsuzaki, Teiichiro*; Ishida, Katsuhiko*; *; Sakamoto, Shinichi*; *; Tanase, Masakazu; Kato, Mineo; Kurosawa, Kiyoyuki; et al.

Hyperfine Interactions, 118(1-4), p.213 - 215, 1999/00

no abstracts in English

Journal Articles

Muon catalyzed fusion and muon to $^{3}$ He transfer in solid T $_{2}$ studied by X-ray and neutron detection

Matsuzaki, Teiichiro*; Nagamine, Kanetada*; Ishida, Katsuhiko*; *; *; Tanase, Masakazu; Kato, Mineo; Kurosawa, Kiyoyuki; Hashimoto, Masashi; Sugai, Hiroyuki; et al.

Hyperfine Interactions, 118(1-4), p.229 - 234, 1999/00

no abstracts in English

Journal Articles