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Journal Articles

Dense radical formation in L-alanine-3,3,3-d3 and L-alanine-d4 by 1.5 keV soft X-ray irradiation

Nakagawa, Seiko*; Oka, Toshitaka; Fujii, Kentaro*; Yokoya, Akinari*

Radiation Physics and Chemistry, 192, p.109884_1 - 109884_5, 2022/03

Radicals produced in crystalline L-alanine-3,3,3-d3 and L-alanine-d4 were observed by the electron spin resonance (ESR) technique during 1.5 keV soft X-ray irradiation. The line width of the ESR spectra obtained by the soft X-ray irradiation was 1.5 times wider than that of hard X-rays from a previous report, meaning a higher density of radicals. The efficiency of the radical yield by the soft X-ray irradiation was 10$$^{-6}$$ relative to that by $$gamma$$-irradiation. For the soft X-ray irradiation, many radicals will be lost by the efficient radical-radical recombination due to the higher density of the radicals, just as the high-LET irradiation by heavy ions. We concluded that the high LET nature of the lower energy photons leads to the dense radical formation in the crystalline alanine powder.

Journal Articles

Three-dimensional electronic structures and the metal-insulator transition in Ruddlesden-Popper iridates

Yamasaki, Atsushi*; Fujiwara, Hidenori*; Tachibana, Shoichi*; Iwasaki, Daisuke*; Higashino, Yuji*; Yoshimi, Chiaki*; Nakagawa, Koya*; Nakatani, Yasuhiro*; Yamagami, Kohei*; Aratani, Hidekazu*; et al.

Physical Review B, 94(11), p.115103_1 - 115103_10, 2016/11

AA2016-0587.pdf:2.55MB

 Times Cited Count:14 Percentile:64.66(Materials Science, Multidisciplinary)

In this study, we systematically investigate three-dimensional(3D) momentum-resolved electronic structures of Ruddlesden-Popper-type iridium oxides Sr$$_{n+1}$$Ir$$_{n}$$O$$_{3n+1}$$ using soft-X-ray angle-resolved photoemission spectroscopy (SX-ARPES). Our results provide direct evidence of an insulator-to-metal transition that occurs upon increasing the dimensionality of the IrO$$_{2}$$-plane structure. This transition occurs when the spin-orbit-coupled $$j_{eff}$$ = 1/2 band changes its behavior in the dispersion relation and moves across the Fermi energy. By scanning the photon energy over 350 eV, we reveal the 3D Fermi surface in SrIrO$$_{3}$$ and $$k_{z}$$-dependent oscillations of photoelectron intensity in Sr$$_{3}$$Ir$$_{2}$$O$$_{7}$$. To corroborate the physics deduced using low-energy ARPES studies, we propose to utilize SX-ARPES as a powerful complementary technique, as this method surveys more than one whole Brillouin zone and provides a panoramic view of electronic structures.

Journal Articles

Ferromagnetic interlayer coupling in C$$_{60}$$-Co compound/Ni bilayer structure

Matsumoto, Yoshihiro; Sakai, Seiji; Entani, Shiro; Takagi, Yasumasa*; Nakagawa, Takeshi*; Naramoto, Hiroshi*; Avramov, P.; Yokoyama, Toshihiko*

Chemical Physics Letters, 511(1-3), p.68 - 72, 2011/07

 Times Cited Count:5 Percentile:18.35(Chemistry, Physical)

X-ray magnetic circular dichroism (XMCD) spectroscopy was employed to investigate the electronic and magnetic structures of the bilayers of a C$$_{60}$$-Co compound and Ni. A few -several nm thick C$$_{60}$$-Co compound layers on the Ni(111) surface are found to show intense XMCD signals attributed to the localized Co d-spins only with the remanent magnetization of Ni layer. It is suggested that the region of the C$$_{60}$$-Co compound within 3 nm from the interface is ferromagnetically coupled with Ni due to the indirect exchange interaction mediated by C$$_{60}$$, probably relevant to the interlayer charge transfer.

Journal Articles

Event structure and double helicity asymmetry in jet production from polarized $$p + p$$ collisions at $$sqrt{s}$$ = 200 GeV

Adare, A.*; Afanasiev, S.*; Aidala, C.*; Ajitanand, N. N.*; Akiba, Y.*; Al-Bataineh, H.*; Alexander, J.*; Aoki, K.*; Aphecetche, L.*; Armendariz, R.*; et al.

Physical Review D, 84(1), p.012006_1 - 012006_18, 2011/07

 Times Cited Count:25 Percentile:72.31(Astronomy & Astrophysics)

We report on the event structure and double helicity asymmetry ($$A_{LL}$$) of jet production in longitudinally polarized $$p + p$$ collisions at $$sqrt{s}$$ = 200 GeV. Photons and charged particles were measured by the PHENIX experiment. Event structure was compared with the results from PYTHIA event generator. The production rate of reconstructed jets is satisfactorily reproduced with the next-to-leading-order perturbative QCD calculation. We measured $$A_{LL}$$ = -0.0014 $$pm$$ 0.0037 at the lowest $$P_T$$ bin and -0.0181 $$pm$$ 0.0282 at the highest $$P_T$$ bin. The measured $$A_{LL}$$ is compared with the predictions that assume various $$Delta G(x)$$ distributions.

Journal Articles

Identified charged hadron production in $$p + p$$ collisions at $$sqrt{s}$$ = 200 and 62.4 GeV

Adare, A.*; Afanasiev, S.*; Aidala, C.*; Ajitanand, N. N.*; Akiba, Yasuyuki*; Al-Bataineh, H.*; Alexander, J.*; Aoki, Kazuya*; Aphecetche, L.*; Armendariz, R.*; et al.

Physical Review C, 83(6), p.064903_1 - 064903_29, 2011/06

 Times Cited Count:156 Percentile:99.42(Physics, Nuclear)

Transverse momentum distributions and yields for $$pi^{pm}, K^{pm}, p$$, and $$bar{p}$$ in $$p + p$$ collisions at $$sqrt{s}$$ = 200 and 62.4 GeV at midrapidity are measured by the PHENIX experiment at the RHIC. We present the inverse slope parameter, mean transverse momentum, and yield per unit rapidity at each energy, and compare them to other measurements at different $$sqrt{s}$$ collisions. We also present the scaling properties such as $$m_T$$ and $$x_T$$ scaling and discuss the mechanism of the particle production in $$p + p$$ collisions. The measured spectra are compared to next-to-leading order perturbative QCD calculations.

Journal Articles

Azimuthal correlations of electrons from heavy-flavor decay with hadrons in $$p+p$$ and Au+Au collisions at $$sqrt{s_{NN}}$$ = 200 GeV

Adare, A.*; Afanasiev, S.*; Aidala, C.*; Ajitanand, N. N.*; Akiba, Yasuyuki*; Al-Bataineh, H.*; Alexander, J.*; Aoki, Kazuya*; Aphecetche, L.*; Aramaki, Y.*; et al.

Physical Review C, 83(4), p.044912_1 - 044912_16, 2011/04

 Times Cited Count:8 Percentile:52.71(Physics, Nuclear)

Measurements of electrons from the decay of open-heavy-flavor mesons have shown that the yields are suppressed in Au+Au collisions compared to expectations from binary-scaled $$p+p$$ collisions. Here we extend these studies to two particle correlations where one particle is an electron from the decay of a heavy flavor meson and the other is a charged hadron from either the decay of the heavy meson or from jet fragmentation. These measurements provide more detailed information about the interaction between heavy quarks and the quark-gluon matter. We find the away-side-jet shape and yield to be modified in Au+Au collisions compared to $$p+p$$ collisions.

Journal Articles

Measurement of neutral mesons in $$p$$ + $$p$$ collisions at $$sqrt{s}$$ = 200 GeV and scaling properties of hadron production

Adare, A.*; Afanasiev, S.*; Aidala, C.*; Ajitanand, N. N.*; Akiba, Y.*; Al-Bataineh, H.*; Alexander, J.*; Aoki, K.*; Aphecetche, L.*; Armendariz, R.*; et al.

Physical Review D, 83(5), p.052004_1 - 052004_26, 2011/03

 Times Cited Count:149 Percentile:98.49(Astronomy & Astrophysics)

The PHENIX experiment at RHIC has measured the invariant differential cross section for production of $$K^0_s$$, $$omega$$, $$eta'$$ and $$phi$$ mesons in $$p + p$$ collisions at $$sqrt{s}$$ = 200 GeV. The spectral shapes of all hadron transverse momentum distributions are well described by a Tsallis distribution functional form with only two parameters, $$n$$ and $$T$$, determining the high $$p_T$$ and characterizing the low $$p_T$$ regions for the spectra, respectively. The integrated invariant cross sections calculated from the fitted distributions are found to be consistent with existing measurements and with statistical model predictions.

JAEA Reports

Long term treatment of waste TBP/n-dodecane with steam reforming system

Sone, Tomoyuki; Nakagawa, Akinori; Koyama, Hayato; Gunji, Kiyoshi; Nonaka, Kazuharu; Sasaki, Toshiki; Tashiro, Kiyoshi; Yamashita, Toshiyuki

JAEA-Technology 2009-023, 33 Pages, 2009/06

JAEA-Technology-2009-023.pdf:8.11MB

Steam reforming (SR) method consists of the gasification process in which organics are vaporized and decomposed with superheated steam and the oxidation process in which vaporized organics are decomposed by oxidizing reaction with heated air. 2,500L of waste TBP/n-dodecane contaminated with uranium was treated using the demonstration scale steam reforming system to examine the performance of the system. Results obtained in this study show that the temperature in the SR system was controlled under the self-regulation temperature, the concentration of CO and NOx in the off-gas were controlled less than 100ppm and 250ppm respectively, the distribution ratio of uranium to off-gas treatment system was under 0.12% and the gasification ratio of waste TBP was more than 99%. This long-term waste treatment test has demonstrated that the SR system can safely and effectively reduce the volume of the waste.

Journal Articles

X-ray absorption spectroscopy and magnetic circular dichroism in codeposited C$$_{60}$$-Co films with giant tunnel magnetoresistance

Matsumoto, Yoshihiro; Sakai, Seiji; Takagi, Yasumasa*; Nakagawa, Takeshi*; Yokoyama, Toshihiko*; Shimada, Toshihiro*; Mitani, Seiji*; Naramoto, Hiroshi*; Maeda, Yoshihito

Chemical Physics Letters, 470(4-6), p.244 - 248, 2009/03

 Times Cited Count:17 Percentile:54.64(Chemistry, Physical)

Electronic and spin states of the codeposited C$$_{60}$$-Co films with large tunnel magnetoresistance (TMR) effect were investigated with the X-ray absorption and magnetic circular dichroism (MCD) spectroscopies. It is revealed that a C$$_{60}$$-Co compound generated in the C$$_{60}$$-Co films shows the clear MCD signal attributed to the spin-polarized Co 3d states hybridized with C$$_{60}$$ $$pi$$ orbitals. The magnetic response of these Co 3d-derived states agrees well with temperature dependence of the observed MR ratios of the granular C$$_{60}$$-Co films. This suggests the incorporation of the spin-polarized Co 3d-derived states of the C$$_{60}$$-Co compound into the observed TMR effect.

Journal Articles

Natural circular dichroism of amino acid films observed in soft X-ray and VUV region using polarizing undulator

Nakagawa, Kazumichi*; Kaneko, Fusae*; Ota, Yoshimi*; Tanaka, Masahito*; Kitada, Tomo*; Agui, Akane; Fujii, Kentaro; Yokoya, Akinari; Watanabe, Kazutoshi*; Yamada, Toru*

Journal of Electron Spectroscopy and Related Phenomena, 144-147, p.271 - 273, 2005/06

 Times Cited Count:12 Percentile:52.38(Spectroscopy)

no abstracts in English

Journal Articles

Chemical evolution of amino acid induced by soft X-ray with synchrotron radiation

Kaneko, Fusae*; Tanaka, Masahito*; Narita, Satoru*; Kitada, Tomo*; Matsui, Takahiro*; Nakagawa, Kazumichi*; Agui, Akane; Fujii, Kentaro; Yokoya, Akinari

Journal of Electron Spectroscopy and Related Phenomena, 144-147, p.291 - 294, 2005/06

 Times Cited Count:18 Percentile:65.08(Spectroscopy)

no abstracts in English

Journal Articles

First observation of natural circular dichroism for biomolecules in soft X-ray region studied with a polarizing undulator

Tanaka, Masahito*; Nakagawa, Kazumichi*; Agui, Akane; Fujii, Kentaro; Yokoya, Akinari

Physica Scripta, T115, p.873 - 876, 2005/00

no abstracts in English

Journal Articles

Oxygen K-edge X-ray absorption near edge structures (XANES) of sublimated films of amino acids

Tanaka, Masahito*; Nakagawa, Kazumichi*; Koketsu, Toshiyuki*; Agui, Akane; Yokoya, Akinari

Journal of Synchrotron Radiation, 8(Part2), p.1009 - 1011, 2001/03

Amino acid molecules are known to be in the state of so-called "zwitter-ion" in solid phase and its extremely low vapour pressure makes ultra high vacuum experiment such as the XANES experiment possible. Recently, C-K edge XANES spectra of aromatic amino acids were studied experimentally and theoretically. Here we selected oxygen K-edge for XANES study of amino acids. From the view point of K-edge XANES study in amino acids, oxygen is interesting because its chemical states have the wealth of variety. A carboxylic group on the $$alpha$$ carbon is in the state of carboxylic anion -COO-, while carboxylic group in side-chain stays on -COOH, and some amino acids have -OH group in side-chain. Due to this variety of chemical environment, we can expect characteristic chemical shift for each oxygen atom in various amino acids. In this paper, we report a result of oxygen K-edge XANES spectra of amino acids (glycine, L-a-alanine, b-alanine, L-serine, L-asparic acid and L-tyrosine) films. We discuss the details of spectra on the basis of DV-X$$alpha$$ calculation.

Oral presentation

Soft X-ray natural circular dichroism of amino acids

Nakagawa, Kazumichi*; Tanaka, Masahito*; Izumi, Yudai*; Agui, Akane; Yokoya, Akinari; Fujii, Kentaro; Muro, Takayuki*; Matsushita, Tomohiro*

no journal, , 

no abstracts in English

Oral presentation

Analysis of magnetic properties in C60-Co nanogranular thin film by XMCD spectroscopy

Matsumoto, Yoshihiro; Sakai, Seiji; Naramoto, Hiroshi*; Takagi, Yasumasa*; Nakagawa, Takeshi*; Shimada, Toshihiro*; Yokoyama, Toshihiko*; Maeda, Yoshihito

no journal, , 

no abstracts in English

Oral presentation

Giant TMR effect and spin states of C$$_{60}$$-Co thin films

Sakai, Seiji; Matsumoto, Yoshihiro; Sugai, Isamu*; Mitani, Seiji*; Takanashi, Koki; Takagi, Yasumasa*; Nakagawa, Takeshi*; Yokoyama, Toshihiko*; Shimada, Toshihiro*; Maeda, Yoshihito

no journal, , 

no abstracts in English

Oral presentation

Electronic and spin states and giant tunnel magnetoresistance effect in C$$_{60}$$-Co hybrid films

Sakai, Seiji; Matsumoto, Yoshihiro; Sugai, Isamu*; Mitani, Seiji*; Takanashi, Koki; Takagi, Yasumasa*; Nakagawa, Takeshi*; Yokoyama, Toshihiko*; Shimada, Toshihiro*; Naramoto, Hiroshi*; et al.

no journal, , 

no abstracts in English

Oral presentation

Soft X-ray circular dichroism study of electronic and magnetic states in C$$_{60}$$-Co mixture film

Matsumoto, Yoshihiro; Sakai, Seiji; Naramoto, Hiroshi*; Nakagawa, Takeshi*; Takagi, Yasumasa*; Yokoyama, Toshihiko*; Takanashi, Koki; Mitani, Seiji*; Shimada, Toshihiro*; Maeda, Yoshihito

no journal, , 

no abstracts in English

Oral presentation

Electronic and magnetic states of codeposited C$$_{60}$$-Co films with giant tunnel magnetoresistance effect

Matsumoto, Yoshihiro; Sakai, Seiji; Naramoto, Hiroshi*; Nakagawa, Takeshi*; Takagi, Yasumasa*; Yokoyama, Toshihiko*; Shimada, Toshihiro*; Mitani, Seiji*; Takanashi, Koki; Maeda, Yoshihito

no journal, , 

no abstracts in English

Oral presentation

X-ray magnetic circular dichroism of codeposited C60-Co films with giant tunnel magnetoresistance

Matsumoto, Yoshihiro; Sakai, Seiji; Naramoto, Hiroshi*; Nakagawa, Takeshi*; Takagi, Yasumasa*; Yokoyama, Toshihiko*; Hirao, Norie; Baba, Yuji; Shimada, Toshihiro*; Maeda, Yoshihito

no journal, , 

Recently, we have found that the codeposited C60-Co films where Co nanoparticles are dispersed into the matrix of the C60-Co compound show large tunnel magnetoresistanene (TMR) effects at low temperatures. The observed MR ratios cannot be explained by a spin-polarization of crystalline Co, so it is expected that the C60-Co compound mediates an enhancing effects to the spin-dependent transport in the films. In the present work, we have investigated the spin states of the C60-Co films by X-ray magnetic circular dichroism spectroscopy. As the results, MCD spectra of the C60-Co compound show the sensitivity to the sample temperature, which is consistent to the temperature dependence of MR ratios. This indicates clearly that spin-polarized states of the C60-Co compound influences the degree of spin-dependent transport in the films.

34 (Records 1-20 displayed on this page)