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Journal Articles

Layered structure in the crystalline adsorption layer and the leaching process of poly(vinyl alcohol) revealed by neutron reflectivity

Miyazaki, Tsukasa*; Miyata, Noboru*; Arima, Hiroshi*; Kira, Hiroshi*; Ouchi, Keiichi*; Kasai, Satoshi*; Tsumura, Yoshihiro*; Aoki, Hiroyuki

Langmuir, 37(32), p.9873 - 9882, 2021/08

 Times Cited Count:0 Percentile:0(Chemistry, Multidisciplinary)

Journal Articles

Practical effects of pressure-transmitting media on neutron diffraction experiments using Paris-Edinburgh presses

Hattori, Takanori; Sano, Asami; Machida, Shinichi*; Ouchi, Keiichi*; Kira, Hiroshi*; Abe, Jun*; Funakoshi, Kenichi*

High Pressure Research, 40(3), p.325 - 338, 2020/09

 Times Cited Count:1 Percentile:32.18(Physics, Multidisciplinary)

To understand the practical effects of pressure-transmitting media (PTM) on neutron diffraction using Paris-Edinburgh presses, diffraction patterns of MgO were collected to approximately 20 GPa using PTMs of Pb, AgCl, 4:1 methano-ethanol (ME) mixture with and without heating, N$$_2$$, and Ar. Hydrostaticity in the sample chamber estimated from the MgO 220 peak width improves in the order of Pb, AgCl, Ar, ME mixture, N$$_2$$, and the heated ME mixture. Unlike previous results using a diamond anvil cell, the unheated ME mixture is superior to Ar even after freezing, probably due to the cup on the anvil face. Considering these results and the sizable coherent scattering of Ne, which would show good hydrostaticity, we conclude that the ME mixture (preferably the heated one) is the best PTM in neutron experiments up to 20 GPa, while Ar can be substituted when a sample is reactive to alcohols.

Journal Articles

Cryogenic sample environments shared at the MLF, J-PARC

Kawamura, Seiko; Takahashi, Ryuta*; Ishikado, Motoyuki*; Yamauchi, Yasuhiro*; Nakamura, Masatoshi*; Ouchi, Keiichi*; Kira, Hiroshi*; Kambara, Wataru*; Aoyama, Kazuhiro*; Sakaguchi, Yoshifumi*; et al.

Journal of Neutron Research, 21(1-2), p.17 - 22, 2019/05

The Cryogenics and Magnets group in the Sample Environment team is responsible for operation of cryostats and magnets for user's experiments at the MLF in J-PARC. We have introduced a top-loading $$^4$$He cryostat, a bottom-loading $$^3$$He cryostat, a dilution refrigerator insert and a superconducting magnet. The frequency of use of them dramatically becomes higher in these two years, as the beam power and the number of proposal increase. To respond such situation, we have made efforts to enhance performance of these equipment as follows. The $$^3$$He cryostat originally involves an operation software for automatic initial cooling down to the base temperature and automatic re-charge of $$^3$$He. Recently we made an additional program for automatic temperature control with only the sorb heater. Last year, a new outer vacuum chamber of the magnet with an oscillating radial collimator (ORC) was fabricated. The data quality was drastically improved by introducing this ORC so that the magnet can be used even for the inelastic neutron scattering experiments.

Journal Articles

Sample environment at the J-PARC MLF

Kawamura, Seiko; Oku, Takayuki; Watanabe, Masao; Takahashi, Ryuta; Munakata, Koji*; Takata, Shinichi; Sakaguchi, Yoshifumi*; Ishikado, Motoyuki*; Ouchi, Keiichi*; Hattori, Takanori; et al.

Journal of Neutron Research, 19(1-2), p.15 - 22, 2017/11

Sample environment (SE) team at the Materials and Life Science Experimental Facility (MLF) in J-PARC has worked on development and operation of SE equipment and devices. All the members belong to one sub-team at least, such as Cryogenic and magnet, High temperature, High pressure, Soft matter and special environment including Pulse magnet, Hydrogen environment, Light irradiation and $$^3$$He spin filter. Cryostats, a magnet, furnaces, a VX-6-type Paris-Edinburgh press and a prototype of a Spin-Exchange Optical Pumping (SEOP) based $$^3$$He spin filter for polarized neutron beam experiments are in operation. Furthermore, a prototype of compact power supply for a pulsed magnet system is currently developed. In the J-PARC Research Building, several pieces of equipment for softmatter research such as a rheometer and a gas and vapor adsorption measurement instrument have been prepared.

Journal Articles

Overview of high-pressure neutron beamline, PLANET, and practical aspects of the experiments

Hattori, Takanori; Sano, Asami; Arima, Hiroshi*; Funakoshi, Kenichi*; Abe, Jun*; Machida, Shinichi*; Okazaki, Nobuo*; Ouchi, Keiichi*; Inamura, Yasuhiro

Koatsuryoku No Kagaku To Gijutsu, 26(2), p.89 - 98, 2016/06

PLANET is a high-pressure neutron beamline constructed at pulsed-neutron source in Materials and Life Science Facility (MLF) in J-PARC. The six-axis multi-anvil press designed for time of flight (TOF) neutron diffraction experiments enables routine data collection at high pressures and high temperatures up to 10 GPa and 2000 K, respectively. To obtain clean data, the beamline is equipped with the incident slits and receiving collimators that eliminate parasitic scattering from the high-pressure cell. The high performance of the diffractometer for the resolution ($$Delta d/d$$ $$sim$$ 0.6%) and the accessible d-spacing range (0.2 - 8.4 ${AA}$) together with low-parasitic scattering characteristics enables precise structure determination of crystals and liquids under high pressure and temperature conditions.

Journal Articles

Maintenance activities of instrumentation control device at JRR-3

Isaka, Koji; Terunuma, Noriaki; Ouchi, Satoshi; Oki, Keiichi; Suwa, Masayuki

Nihon Hozen Gakkai Dai-6-Kai Gakujutsu Koenkai Yoshishu, p.279 - 282, 2009/08

As the modified JRR-3 has been operated for 18 years, it is necessary to be maintained for keeping the safe and stable operation. The review of maintenance activity is constantly performed for the step-by-step update of facilities and the improvement of the maintenance method and so on. Our investigation of the maintenance activity about the instrumentation and control device of modified JRR-3 is presented.

Journal Articles

Photoelectron-photoion coincidence momentum imaging for dissociative ionization of ethanol in intense laser fields

Hosaka, Koichi; Itakura, Ryuji; Yokoyama, Keiichi; Yamanouchi, Kaoru*; Yokoyama, Atsushi

Chemical Physics Letters, 475(1-3), p.19 - 23, 2009/06

 Times Cited Count:11 Percentile:35.14(Chemistry, Physical)

In intense laser fields, molecules are decomposed into fragments through a number of competing dissociative ionization pathways. We investigate the dissociative ionization dynamics of ethanol in intense laser fields with photoelectron-photoion coincidence momentum imaging. The channel-specific photoelectron spectra reveal the electronic states prepared just after ionization, depending both on the decomposition pathways and on the temporal profile of laser pulses.

Journal Articles

Quantum control of molecular vibration and rotation toward the isotope separation

Yokoyama, Keiichi; Matsuoka, Leo; Kasajima, Tatsuya; Tsubouchi, Masaaki; Yokoyama, Atsushi

Proceedings of 5th Asian Symposium on Intense Laser Science (ASILS-5), p.113 - 119, 2009/05

The current status of the fundamental research for the quantum control conducted at Kansai Photon Science Institute are reported. In particular, the experimental studies on vibrational control of diatomic molecules, the nitrogen molecules and the iodine molecules, and the theoretical study on the rotational control of the diatomic molecule, the cesium iodide molecule (CsI), are introduced. For the study of vibrational control of N$$_{2}$$, the vibration selective excitation with extremely broadband white light pulses is demonstrated by tuning the time interval of a linearly chirped white light pulse pair. For the study of vibrational control of I$$_{2}$$, the direction control of stimulated impulsive Raman transition is demonstrated by changing the sign of the chirp rate. For the study of rotational control of CsI, the isotope-selective population distribution transfer is demonstrated numerically using frequency comb in the terahertz-wave region.

Oral presentation

Photoelectron-photoion coincidence momentum imaging for dissociative ionization in intense laser fields

Hosaka, Koichi; Itakura, Ryuji; Yokoyama, Keiichi; Yamanouchi, Kaoru*; Yokoyama, Atsushi

no journal, , 

When molecules are exposed to intense laser fields, dissociative ionization is efficiently induced and several decomposition pathways competes. The present study aims at revealing the correlation between the electronic states just after ionization and the following dissociation process. The photoelectron-photoion coincidence momentum imaging (PEPICO-MI) technique enables us to detect photoelectrons and photoions produced in a single event simultaneously. We applied PEPICO-MI to dissociative ionization of ethanol (C$$_{2}$$H$$_{5}$$OH), whose branching ratio varies as a function of the laser pulse duration. When ethanol molecules are irradiated with a short laser pulse, photoelectron images strongly depend on the correlated product ions.

Oral presentation

Dissociative ionization dynamics of ethanol in intense laser fields by photoelectron-photoion coincidence momentum imaging

Hosaka, Koichi; Itakura, Ryuji; Yokoyama, Keiichi; Yamanouchi, Kaoru*; Yokoyama, Atsushi

no journal, , 

In intense laser fields, molecules are decomposed into fragments through a number of competing dissociative ionization pathways. We investigate the dissociative ionization dynamics of ethanol in intense laser fields with photoelectron-photoion coincidence momentum imaging. The channel-specific photoelectron spectra reveal the electronic states prepared just after ionization, depending both on the decomposition pathways and on the temporal profile of laser pulses.

Oral presentation

Dissociative ionization of ethanol in intense laser fields by photoelectron-photoion coincidence momentum imaging

Hosaka, Koichi; Itakura, Ryuji; Yokoyama, Keiichi; Yamanouchi, Kaoru*; Yokoyama, Atsushi

no journal, , 

In intense laser fields, molecules are decomposed into fragments through a number of competing dissociative ionization pathways. We investigate the dissociative ionization dynamics of ethanol in intense laser fields with photoelectron-photoion coincidence momentum imaging. The channel-specific photoelectron spectra reveal the electronic states prepared just after ionization, depending both on the decomposition pathways and on the temporal profile of laser pulses.

Oral presentation

Dissociative ionization dynamics of ethanol in intense laser fields studied by photoelectron-photoion coincidence momentum imaging

Hosaka, Koichi; Itakura, Ryuji; Yokoyama, Keiichi; Yamanouchi, Kaoru*; Yokoyama, Atsushi

no journal, , 

In intense laser fields, molecules are decomposed into fragments through a number of competing dissociative ionization pathways. We investigate the dissociative ionization dynamics of ethanol in intense laser fields with photoelectron-photoion coincidence momentum imaging. The channel-specific photoelectron spectra reveal the electronic states prepared just afterionization, depending both on the decomposition pathways and on the temporal profile of laserpulses.

Oral presentation

Fragment momentum specific photoelectron imaging of ethanol in intense laser field

Hosaka, Koichi; Itakura, Ryuji; Yokoyama, Keiichi; Yamanouchi, Kaoru*; Yokoyama, Atsushi

no journal, , 

In intense laser fields, molecules are decomposed into fragments through a number of competing dissociative ionization pathways. We have investigated the dissociative ionization dynamics of ethanol in intense laser fields with photoelectron-photoion coincidence momentum imaging. The fragment momentum specific photoelectron images reveal the correlation between the electronic states prepared just after ionization and the following dissociation dynamics of ethanol cation.

Oral presentation

Intense laser induced electronic excitation in dissociative ionization of ethanol studied by photoelectron-photoion coincidence momentum imaging

Hosaka, Koichi; Itakura, Ryuji; Yokoyama, Keiichi; Yamanouchi, Kaoru*; Yokoyama, Atsushi

no journal, , 

Oral presentation

Fragment ion momentum resolved photoelectron imaging of ethanol in intense laser fields

Hosaka, Koichi; Itakura, Ryuji; Yokoyama, Keiichi; Yamanouchi, Kaoru*; Yokoyama, Atsushi

no journal, , 

no abstracts in English

Oral presentation

Dissociative ionization of oxygen in intense laser fields studied by photoelectron photoion coincidence momentum imaging

Hosaka, Koichi; Itakura, Ryuji; Yokoyama, Keiichi; Yamanouchi, Kaoru*; Yokoyama, Atsushi

no journal, , 

no abstracts in English

Oral presentation

Double pulse generation and detection in THz region; Simplest case of arbitrary pulse shaping

Tsubouchi, Masaaki; Yokoyama, Keiichi; Sugiyama, Akira

no journal, , 

In this study, we examined the double pulse generation of THz pulses which is the simplest example toward the arbitrary pulse shaping. Intrinsic difficulties of THz pulse shaping was found from the double pulse experiment.

Oral presentation

Double pulse generation and detection in THz region; The Simplest case of arbitrary pulse shaping

Tsubouchi, Masaaki; Yokoyama, Keiichi; Sugiyama, Akira

no journal, , 

no abstracts in English

Oral presentation

Theoretical study on the isotope-selective vibrational ladder climbing by consecutive stimulated Raman transitions

Kasajima, Tatsuya; Tsubouchi, Masaaki; Matsuoka, Leo; Yokoyama, Keiichi; Yokoyama, Atsushi

no journal, , 

no abstracts in English

Oral presentation

Theoretical study on the cascade excitation based on pure rotational transition in diatomic molecules

Yokoyama, Keiichi; Matsuoka, Leo; Akagi, Hiroshi; Kasajima, Tatsuya; Tsubouchi, Masaaki

no journal, , 

Pure rotational transition shows evenly spaced line spectra, the rotational comb, when the molecule is diatomic and has a closed-shell electronic structure. Let us consider irradiating an optical frequency comb tuned to the rotational comb. We studied numerically the dynamics of the molecular rotation in such a irradiation. As a result, the dynamics was found to obey the diffusion equation within the quantum mechanics. Also, we found that an isotope-selective excitation based on this scheme is a novel example of coherent control effective even at high temperature.

32 (Records 1-20 displayed on this page)