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Journal Articles

Morphological reproductive characteristics of testes and fertilization capacity of cryopreserved sperm after the Fukushima accident in raccoon (${it Procyon lotor}$)

Komatsu, Kazuki*; Iwasaki, Tsugumi*; Murata, Kosuke*; Yamashiro, Hideaki*; Goh, V. S. T.*; Nakayama, Ryo*; Fujishima, Yohei*; Ono, Takumi*; Kino, Yasushi*; Shimizu, Yoshinaka*; et al.

Reproduction in Domestic Animals, 56(3), p.484 - 497, 2021/03

 Times Cited Count:6 Percentile:98.08(Agriculture, Dairy & Animal Science)

We have established an archive system of livestock and wild animals from the surrounding ex-evacuation zone. Wildlife within the alert zone have been exposed to low-dose-rate (LDR) radiation for a long and continuous time. In this study, we analysed the morphological characteristics of the testes and in vitro fertilization (IVF) capacity of cryopreserved sperm of raccoons from the ex-evacuation zone of the FDNPP accident. This study revealed that the chronic and LDR radiation exposure associated with the FDNPP accident had no adverse effect on the reproductive characteristics and functions of male raccoons.

Journal Articles

Storage characteristics of KBr:Eu$$^{2+}$$ phosphors with radiators by irradiation of fast neutrons

Sakasai, Kaoru; Iwamoto, Yosuke; To, Kentaro; Nakamura, Tatsuya; Takakura, Kosuke; Konno, Chikara

2010 IEEE Nuclear Science Symposium Conference Record (CD-ROM), p.966 - 970, 2010/10

Storage characteristics of KBr:Eu$$^{2+}$$ phosphor were investigated when the phosphor was irradiated by fast neutron with energy of 14.8 MeV. To improve the fast neutron sensitivity, polyethylene (PE) sheets as a proton generator were set in front of the phosphors. The maximum photostimulated luminescence (PSL) yields were obtained at a PE thickness of about 3 mm. These experimental results well agreed with those by Monte Carlo simulation using PHITS code. Estimated PSL yields by $$gamma$$-ray associated with fast neutron fields were negligible. This combination use of such phosphors and PE sheets will be usable for fast neutron monitoring or imaging.

Journal Articles

Fabrication of Cu oxides on single crystal Cu surfaces using hyperthermal O$$_{2}$$ molecular beams

Okada, Michio*; Moritani, Kosuke*; Vattuone, L.*; Savio, L.*; Teraoka, Yuden; Kasai, Toshio*; Rocca, M.*

Metal Oxide Nanostructures and Their Applications, 1, p.205 - 237, 2010/03

The use of hyperthermal O$$_{2}$$ molecular beams may improve the quality of thin film growth, for example, for organic films, and allow the production of oxide layers at lower crystal temperatures, avoiding contamination problems and reducing film defects. Collision-induced absorption and local heating of the substrate were shown to be indeed effective in inducing oxide nucleation, opening up new possibilities for the production of nanostructured metal oxides. Herein we offer an overview on recent detailed studies of oxygen adsorption and of the initial stages of Cu$$_{2}$$O and CuO formation on low Miller index and vicinal Cu surfaces. We introduce the hyperthermal molecular beam technique and give some details on the experimental apparatuses. We discuss the available data for Cu(100), Cu(410) and Cu(110) and Cu(111), respectively.

Journal Articles

Kinetics of oxygen adsorption and initial oxidation on Cu(110) by hyperthermal oxygen molecular beams

Moritani, Kosuke*; Okada, Michio*; Teraoka, Yuden; Yoshigoe, Akitaka; Kasai, Toshio*

Journal of Physical Chemistry A, 113(52), p.15217 - 15222, 2009/10

 Times Cited Count:11 Percentile:37.48(Chemistry, Physical)

Oxygen adsorption and subsequent oxide formation on Cu(110) using a hyperthermal oxygen molecular beam (HOMB) has been investigated using SR-XPS. The O-uptake curves, which were determined from the evolution of O-1s peaks, indicate that simple Langmuir type kinetics can describe dissociative adsorption of O$$_{2}$$ with an incident energy (Ei) below 0.5eV under oxygen coverage of 0.5 ML. The reaction order dependence on Ei implies two competing dissociation mechanisms, trapping-mediated and directly-activated adsorption. Oxidation at oxygen coverage larger than 0.5 ML proceeds rather effectively using highly energetic HOMB at Ei larger than 1.0 eV. The surface Cu$$_{2}$$O formed with highly-energetic HOMB incidence decomposes with desorbing subsurface oxygen even at room temperature. This indicates that HOMB can induce a meta stable surface structure that cannot be produced in the thermal equilibrium process.

Journal Articles

Reconstruction of Cu(111) induced by a hyperthermal oxygen molecular beam

Moritani, Kosuke*; Okada, Michio*; Teraoka, Yuden; Yoshigoe, Akitaka; Kasai, Toshio*

Journal of Physical Chemistry C, 112(23), p.8662 - 8667, 2008/06

 Times Cited Count:28 Percentile:65.75(Chemistry, Physical)

This paper reports a study on the reconstruction at Cu(111) surface induced by a hyperthermal oxygen molecular beam (HOMB) at room temperature. The HOMB incidence at translational energies larger than 0.5 eV induced surface reconstruction in the oxygen coverage larger than 0.27 ML. On the other hand, long-range-ordered structures were not formed even at the oxygen coverage of 0.4 ML for the backfilling of thermal O$$_{2}$$ at room temperature. The O1s XPS peak for the HOMB incidence at room temperature was resolved into two components, 529.4 and 528.9 eV, at the oxygen coverage larger than 0.27 ML, which can be assigned to the O atoms occupying the threefold hollow sites on the unreconstructed Cu(111) surface and four-coordinated sites on the reconstructed structure, respectively. Annealing the reconstructed surface at 620 K decreased the oxygen coverage to 0.27 ML and induced so-called "29" superstructure.

Journal Articles

Stereodynamics in dissociative adsorption of NO on Si(111)

Hashinokuchi, Michihiro*; Okada, Michio*; Ito, Hironori*; Kasai, Toshio*; Moritani, Kosuke*; Teraoka, Yuden

Physical Review Letters, 100(25), p.256104_1 - 256104_4, 2008/06

 Times Cited Count:16 Percentile:66.98(Physics, Multidisciplinary)

We report results of studies on surface-temperature dependence of steric effects in dissociative adsorption processes of NO molecules on Si(111)-(7$$times$$7) surface by means of X-ray photoemission spectroscopy. Data presented here show that the reactive sticking probability for N-end collisions is larger than that in O-end collisions at an incident energy of 58 meV. Furthermore, this steric preference is quite sensitive to the surface temperature and the surface coverage. These facts reveal that transient surface trapping of NO molecules in a shallow precursor state plays a key role in the initial step of the NO decomposition on the Si(111)-(7$$times$$7) surface.

Journal Articles

New oriented-molecular-beam machine for surface stereochemistry with X-ray photoemission spectroscopy

Okada, Michio*; Hashinokuchi, Michihiro*; Moritani, Kosuke*; Kasai, Toshio*; Teraoka, Yuden

Japanese Journal of Applied Physics, 47(5), p.3686 - 3691, 2008/05

 Times Cited Count:5 Percentile:23.69(Physics, Applied)

An oriented-molecular-beam technique based on the Stark effect of a molecule in an inhomogeneous hexapole electrostatic field is a potential tool for stereochemical control of surface reactions. This technique allows us to select a specific rotational quantum state and also an orientation of a reagent molecule. We have developed a new UHV-compatible oriented-molecular-beam machine. This apparatus is equipped with components for X-ray photoemission spectroscopy (XPS) in order to detect surface-reaction products. In the dissociative adsorption of NO on an Si(111) surface, we found a steric effect in the reactivity by monitoring the products on the surface with the new machine. The N-end collision is more reactive than the O-end collision at an incident energy of 58 meV. To our knowledge, this is the first measurement of the steric effect appearing in the reaction products on the surface.

Journal Articles

Dissociative adsorption of nitric oxide on Si(111)-(7$$times$$7) surface

Hashinokuchi, Michihiro*; Ito, Hironori*; Teraoka, Yuden; Moritani, Kosuke*; Okada, Michio*; Kasai, Toshio*

Japanese Journal of Applied Physics, 47(3), p.1672 - 1676, 2008/03

 Times Cited Count:4 Percentile:19.6(Physics, Applied)

Dissociative adsorption of nitric oxide (NO) on Si(111)-7$$times$$7 surface between 330-600 K was investigated using X-ray photoelectron spectroscopy. The uptake curves of both N and O atoms as a function of NO dose revealed a prominent temperature dependence of dissociative adsorption of NO on an Si(111)-7$$times$$7 surface. The decrease in the rates of dissociative adsorption of NO with increasing surface temperature suggested existence of a precursor state. Additionally, the N/O ratio on the surface changed from 1.0 at 330 K to 1.2 at 600 K. This increasing N/O ratio with increasing surface temperature suggests that an additional reaction path opens at higher surface temperature.

Journal Articles

Unravelling the role of steps in Cu$$_{2}$$O formation via hyperthermal O$$_{2}$$ adsorption at Cu(410)

Okada, Michio*; Vattuone, L.*; Gerbi, A.*; Savio, L.*; Rocca, M.*; Moritani, Kosuke*; Teraoka, Yuden; Kasai, Toshio*

Journal of Physical Chemistry C, 111(46), p.17340 - 17345, 2007/11

 Times Cited Count:18 Percentile:52.86(Chemistry, Physical)

We report a study on the oxidation process of Cu(410) using high-resolution electron energy loss spectroscopy and X-ray photoemission spectroscopy using synchrotron radiation. We demonstrate that a hyperthermal O$$_{2}$$ molecular beam (HOMB) is an efficient tool to fabricate Cu$$_{2}$$O thin film also at room temperature. The efficiency of the Cu$$_{2}$$O formation in the initial stages depends on the angle of incidence of HOMB. Step roughening, acting as a source of mobile precursor Cu adatoms and opening channels for bulk diffusion of the O atoms, is a key feature in determining the Cu$$_{2}$$O formation rate.

Journal Articles

Pressure and temperature dependence of cuprous oxide nucleation on Cu(410)

Okada, Michio*; Vattuone, L.*; Moritani, Kosuke*; Savio, L.*; Teraoka, Yuden; Kasai, Toshio*; Rocca, M.*

Journal of Physics; Condensed Matter, 19(30), p.305022_1 - 305022_7, 2007/08

 Times Cited Count:8 Percentile:39.89(Physics, Condensed Matter)

We studied the oxidation of Cu(410) for thermal O$$_{2}$$ exposure and using High-resolution Electron Energy-loss Spectroscopy. Cu$$_{2}$$O is identified by loss peaks at 19 meV and 79 meV. By monitoring the intensity of the latter, we find that Cu$$_{2}$$O formation depends strongly on surface temperature and on O$$_{2}$$ pressure and is kinetically limited by the impinging O$$_{2}$$ flux. Thermally activated step roughening, leading to detachment of Cu adatoms from the step edge, acts as a source of mobile Cu atoms allowing for subsequent nucleation of Cu$$_{2}$$O patches.

Journal Articles

Effects of vibrational and rotational excitations on the dissociative adsorption of O$$_{2}$$ on Cu surfaces

Moritani, Kosuke*; Tsuda, Muneyuki*; Teraoka, Yuden; Okada, Michio*; Yoshigoe, Akitaka; Fukuyama, Tetsuya*; Kasai, Toshio*; Kasai, Hideaki*

Journal of Physical Chemistry C, 111(27), p.9961 - 9967, 2007/07

 Times Cited Count:11 Percentile:39.31(Chemistry, Physical)

We report an X-ray photoemission study of the dissociative adsorption of O$$_{2}$$ at Cu(111), (001), and (110) surfaces with an O$$_{2}$$ molecular beam generated with a variable temperature nozzle. The O-uptake curves, which are produced from precisely measured O-1s peaks, indicate that the dissociative absorption is enhanced as the nozzle temperature is increased up to 1000 K for the normal incidence of O$$_{2}$$ at a kinetic energy of 0.5 eV. However, further increasing the nozzle temperature to 1400 K reduces the probability of dissociativeadsorption. These results suggest that vibrational excitations of incident O$$_{2}$$ assist dissociative adsorption while rotational excitations hinder it.

Journal Articles

X-ray photoemission study of the temperature-dependent CuO formation on Cu(410) using an energetic O$$_{2}$$ molecular beam

Okada, Michio*; Vattuone, L.*; Moritani, Kosuke*; Savio, L.*; Teraoka, Yuden; Kasai, Toshio*; Rocca, M.*

Physical Review B, 75(23), p.233413_1 - 233413_4, 2007/06

 Times Cited Count:34 Percentile:78.14(Materials Science, Multidisciplinary)

We studied the oxidation of Cu(410) using X-ray photoemission spectroscopy performed with synchrotron radiation. We demonstrate that a hyperthermal O$$_{2}$$ molecular beam is an efficient tool to fabricate Cu oxide thin films at room temperature (RT) and even lower temperatures. At RT, mainly Cu$$_{2}$$O forms. At around 100 K, CuO nucleation also takes place; this is noteworthy, since this moiety is usually produced only at much higher $$T$$ and ambient pressure.

Journal Articles

Protective layer formation during oxidation of Cu$$_{3}$$Au(100) using hyperthermal O$$_{2}$$ molecular beam

Okada, Michio*; Hashinokuchi, Michihiro*; Fukuoka, Masayuki*; Kasai, Toshio*; Moritani, Kosuke*; Teraoka, Yuden

Applied Physics Letters, 89(20), p.201912_1 - 201912_3, 2006/11

 Times Cited Count:24 Percentile:65.01(Physics, Applied)

Oxidation of Cu$$_{3}$$Au(100) using a hyperthermal O$$_{2}$$ molecular beam (HOMB) was investigated by X-ray photoemission spectroscopy in conjunction with a synchrotron light source. From the incident energy dependence of the O-uptake curve, it was determined that the dissociative adsorption of O$$_{2}$$ implies a higher activation barrier and therefore less reactivity due to the Au alloying. The dissociative adsorption progresses with the Cu segregation on the surface. No prominent growth of Cu$$_{2}$$O even for 2 eV HOMB suggests that the Au-alloying of Cu can serve as a protective layer against further oxidation into the bulk.

Journal Articles

Comparative study of oxidation on Cu and Cu$$_{3}$$Au surfaces with a hyperthermal O$$_{2}$$ molecular beam

Okada, Michio*; Moritani, Kosuke; Fukuyama, Tetsuya*; Mizutani, Hironori*; Yoshigoe, Akitaka; Teraoka, Yuden; Kasai, Toshio*

Surface Science, 600(18), p.4228 - 4232, 2006/09

 Times Cited Count:19 Percentile:64.34(Chemistry, Physical)

Dissociative adsorption of hyperthermal O$$_{2}$$ molecules on Cu$$_{3}$$Au(100) was investigated by X-ray photoemission spectroscopy in conjunction with a synchrotron light source. Comparing the O-uptake curve on Cu$$_{3}$$Au with that on Cu, it was found that the dissociative adsorption of O$$_{2}$$ is more activated (less reactive) due to Au alloying. The low-energy electron-diffraction (LEED) pattern of c(2$$times$$2) for the clean surface turned into the (1$$times$$1) LEED pattern during the oxidation by hyperthermal O$$_{2}$$ molecular beam, suggesting that the O adsorption induces the Cu-atom segregation on the surface.

Journal Articles

The Azimuthal dependent oxidation process on Cu(110) by energetic oxygen molecules

Moritani, Kosuke; Okada, Michio*; Fukuyama, Tetsuya*; Teraoka, Yuden; Yoshigoe, Akitaka; Kasai, Toshio*

European Physical Journal D, 38(1), p.111 - 115, 2006/04

 Times Cited Count:14 Percentile:55.7(Optics)

We report a study on the oxidation process induced by a hyperthermal oxygen molecular beam (HOMB) on Cu(110) using X-ray photoemission spectroscopy in conjunction with a synchrotron radiation source. The oxidation process induced by energetic O$$_{2}$$ beams on Cu(110), depending on the azimuthal angle of incidence, suggests that the -Cu-O- added row structure has a role in inhibiting adsorption as a steric obstacle for incident O$$_{2}$$ molecules.

JAEA Reports

Rotational states of CH$$_{3}$$CN selected using hexapole electric field (Cooperative research)

Hashinokuchi, Michihiro*; Okada, Michio*; Kasai, Toshio*; Moritani, Kosuke; Teraoka, Yuden

JAEA-Research 2005-002, 16 Pages, 2006/01

JAEA-Research-2005-002.pdf:0.91MB

The dynamical processes such as the energy transfer of a molecule to a surface, etc. play an important role in surface chemical reactions. An oriented-molecular-beam method can provide a great insight into these processes. We have developed a UHV-compatible oriented-molecular-beam machine. In the present study, we performed rotational-state selection of CH$$_{3}$$CN using hexapole electric field. We measured the focusing curve of CH$$_{3}$$CN, which was reproduced by the trajectory simulation including the second-order Stark effect in the inhomogeneous hexapole electric field. The expected orientation distributions suggest our ability to control the molecular orientation in surface reactions.

Journal Articles

Surface chemical reaction dynamics illuminated by high brilliance and high energy-resolution synchrotron radiation; In-situ photoemission spectroscopy for surface oxidation induced by supersonic O$$_{2}$$ molecular beams

Teraoka, Yuden; Yoshigoe, Akitaka; Moritani, Kosuke; Takakuwa, Yuji*; Ogawa, Shuichi*; Ishizuka, Shinji*; Okada, Michio*; Fukuyama, Tetsuya*; Kasai, Toshio*

Hoshako, 18(5), p.298 - 309, 2005/09

Representative research results in surface reaction dynamics, performed at a surface chemistry experimental station installed in the JAEA soft X-ray beamline in the SPring-8, were reviewed. As a research result in JAEA, SiO desorption mechanisms in the Si(001) oxidation at high temperature were introduced. As a collaboration with Osaka University on oxidation reaction dynamics of Cu, collision-induced atom absorption process was introduced. As a collaboration with Tohoku University on Ti(0001) oxidation reaction dynamics, it was introduced that two peaks, found in an incident energy dependence of initial sticking probability, were corresponding to potential energy barriers of dissociative adsorption of O$$_{2}$$ molecules.

Journal Articles

Photoemission study of the translational energy induced oxidation processes on Cu(111)

Moritani, Kosuke; Okada, Michio*; Sato, Seiichi*; Goto, Seishiro*; Kasai, Toshio*; Yoshigoe, Akitaka; Teraoka, Yuden

Journal of Vacuum Science and Technology A, 22(4), p.1625 - 1630, 2004/08

 Times Cited Count:21 Percentile:62.19(Materials Science, Coatings & Films)

We studied the oxidation of Cu{111} surface with a hyperthermal O$$_{2}$$ molecular beam (HOMB) using X-ray photoemission spectroscopy (XPS) in conjunction with a synchrotron radiation (SR) source. The efficiency of oxidation with 0.6-eV-HOMB is higher thab that with 2.3-eV-HOMB under $$theta$$ $$leq$$ 0.5ML. Ont the other hand, further oxidation occurs rather inefficiency under $$theta$$ $$geq$$ 0.5ML. In this region, efficiency of oxidation with 2.3-eV-HOMB is higher than 0.6-eV-HOMB. We found that such slow oxidation process of Cu can be interpreted in terms of a collision-induced-adsorption mechanism. These results suggest that we can control the oxidation process of Cu by using HOMB.

Journal Articles

Tuning of dissociative-adsorption processes on Cu{1 0 0} by controlling the kinetic energy of the impinging O$$_{2}$$ molecule

Okada, Michio*; Moritani, Kosuke; Yoshigoe, Akitaka; Teraoka, Yuden; Nakanishi, Hiroshi*; Di$~n$o, W. A.*; Kasai, Hideaki*; Kasai, Toshio*

Chemical Physics, 301(2-3), p.315 - 320, 2004/06

 Times Cited Count:14 Percentile:43.13(Chemistry, Physical)

O$$_{2}$$ molecules adsorb dissociatively on Cu{1 0 0} surfaces to form the oxygen-saturated surface with the coverage of 0.5 ML. It has been found that the oxidation has proceeded more than 0.5 ML by using 2.3-eV-O$$_{2}$$ molecular beams. The kinetics of the adsorption reaction was the first order. This reveals that the collision-induced adsorption results in the adsorption of only one oxygen atom. On the other hand, the reaction kinetics showed the second order in the case of 0.6-eV-O$$_{2}$$ incidence. This implies that tentative molecular adsorption takes place in such low collision energy case.

Journal Articles

Actively controlled oxidation of Cu{001} with hyperthermal O$$_{2}$$ molecular beam

Okada, Michio*; Moritani, Kosuke; Goto, Seishiro*; Kasai, Toshio*; Yoshigoe, Akitaka; Teraoka, Yuden

Journal of Chemical Physics, 119(14), p.6994 - 6997, 2003/10

 Times Cited Count:42 Percentile:79.43(Chemistry, Physical)

The oxidation of Cu(001) with hyperthermal O$$_{2}$$ molecular beams was investigated using X-ray photoemission spectroscopy in conjunction with a synchrotron light source. The efficiency of oxidation is higher than that with ambient thermal O$$_{2}$$. Further oxidation under oxygen coverage larger than 0.5 ML occurs rather inefficiently even for the 2.3 eV beam irradiation. We found such slow oxidation of Cu corresponding to the initial stage of the Cu$$_{2}$$O formation can be interpreted in terms of a collision-induced-adsorption mechanism. The kinetics of the dissociative adsorption is well described using the first order kinetics in a simple Langmuir-type adsorption model.

53 (Records 1-20 displayed on this page)