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論文

Quantitative hydrogen state analysis in the leached layer of soda-lime-silica glass by combination of nuclear reaction analysis and C$$_{60}$$-X-ray photoelectron spectroscopy

末原 道教*; 山本 雄一*; 小倉 正平*; 福谷 克之

Journal of Non-Crystalline Solids, 574, p.121160_1 - 121160_4, 2021/12

The effects of acid treatment on the surface layer of soda-lime-silica glasses were investigated by nuclear reaction analysis (NRA) and C$$_{60}$$-X-ray photoelectron spectroscopy (XPS) in a depth-resolved manner. As the time of treatment with HCl increased, the amount of H increased and was distributed in a region at a depth of almost 150 nm. In the near-surface region, however, the damage due to $$^{15}$$N$$^{2+}$$ beam irradiation for conducting the NRA was found to be substantial as observed by the fast decay of signal intensity with increasing ion dose. The depletion of sodium, magnesium, and calcium in the surface layer was examined by C$$_{60}$$-XPS. Sodium was depleted at a depth of 150 nm by the acid treatment, but the depletion of magnesium and calcium occurred at a depth within approximately 30 nm. Assuming the ion exchange reaction between the alkaline and alkaline earth elements with H$$_{3}$$O$$^{+}$$, the Si-OH concentration profile was evaluated from the depletion profiles of sodium, magnesium, and calcium. From the difference between the Si-OH profile and H distribution obtained by NRA, the H$$_{2}$$O/Si-OH ratio in the leached layer was estimated at 1.3.

論文

Focusing and spin polarization of atomic hydrogen beam

長屋 勇輝*; 中津 裕貴*; 小倉 正平*; 島崎 紘太*; 植田 寛和; 武安 光太郎*; 福谷 克之

Journal of Chemical Physics, 155(19), p.194201_1 - 194201_6, 2021/11

We have developed a spin-polarized-hydrogen beam with a hexapole magnet. By combining the beam chopper and pulsed laser ionization detection, the time-of-flight of the hydrogen beam was measured, and the dependence of the beam profile on the velocity was acquired, which was consistent with the beam trajectory simulations. The spin polarization of the beam was analyzed by using the Stern-Gerlach-type magnet in combination with the spatial scan of the detection laser. The spin polarization was about 95% at a focusing condition due to the hexapole magnet. The polarization was, on the other hand, reduced to about 70% for the beam at higher velocities, which is consistent with simulation results.

論文

Direct measurement of fast ortho-para conversion of molecularly chemisorbed H$$_{2}$$ on Pd(210)

植田 寛和; 笹川 裕矢*; Ivanov, D.*; 大野 哲*; 小倉 正平*; 福谷 克之

Physical Review B, 102(12), p.121407_1 - 121407_5, 2020/09

 被引用回数:0 パーセンタイル:6.21(Materials Science, Multidisciplinary)

Pd(210)表面に化学吸着したH$$_{2}$$のオルトーパラ転換を報告する。分子線,光刺激脱離,共鳴多光子イオン化法を用いて水素の回転状態変化を調べた。実験結果から、~2秒の転換時間で転換が起こることが明らかになった。実験結果と過去の理論計算結果を比較することで、2次の摂動による転換メカニズムを支持する。

論文

Hydrogen distribution and electronic structure of TiO$$_{2}$$(110) hydrogenated with low-energy hydrogen ions

大橋 由季*; 長塚 直樹*; 小倉 正平*; 福谷 克之

Journal of Physical Chemistry C, 123(16), p.10319 - 10324, 2019/04

The rutile TiO$$_{2}$$ surface irradiated by hydrogen ions at 0.5 keV was investigated by ultraviolet photoemission spectroscopy, X-ray photoemission spectroscopy, and nuclear reaction analysis. With hydrogen irradiation, an in-gap state (IGS) was formed at $$sim$$0.8 eV below the Fermi level, and the bands were downward bent by 0.5 eV. The H depth profile showed a maximum at about 1 nm, extending to $$sim$$30 nm with an average concentration of 5.6 at. %. Upon annealing at 673 K, the IGS intensity was reduced and H with a coverage of 1.4 monolayer remained in the near-surface region, suggesting stable H occupation of subsurface sites. After an O$$_{2}$$ dose to the H-irradiated surface, although the IGS intensity was substantially reduced, the hydrogen distribution was found to be unchanged.

口頭

Rotational-state distribution and ortho-para conversion of molecularly chemisorbed H$$_{2}$$ on Pd(210)

植田 寛和; 笹川 裕矢*; Ivanov, D.*; 大野 哲*; 小倉 正平*; 福谷 克之

no journal, , 

Imperfections of the surface, such as steps, are known to affect adsorption and reaction processes. While hydrogen typically chemisorbs dissociatively on a flat metal surface, it is known that hydrogen can molecularly chemisorb on stepped surfaces, such as Ni(510) and Pd(210), in which the potential is expected to be highly anisotropic, unlike the case of physisorption. The anisotropic potential would modify the rotational state of H$$_{2}$$ and promote ortho-para (o-p) conversion. For the system of H$$_{2}$$/Pd(210), the conversion time of ~1 sec was predicted based on the measurement on rotational-state-selective thermal desorption of H$$_{2}$$ (J=0 and J=1). The predicted value is indeed much shorter than those in previously reported physisorption systems. In this contribution, to further probe the rotational state and conversion of molecularly chemisorbed H$$_{2}$$, a combination of a pulsed molecular beam, photo-stimulated desorption and resonance-enhanced multiphoton ionization techniques is used. We will present the rotational state distribution of photo-desorbed H$$_{2}$$, and the o-p conversion process of molecularly chemisorbed H$$_{2}$$ will be discussed.

口頭

Pd(210)表面における水素分子のオルト-パラ転換研究

植田 寛和; 笹川 裕矢*; Ivanov, D.*; 大野 哲*; 小倉 正平*; 福谷 克之

no journal, , 

一般的に平坦な金属表面では水素分子は解離吸着をするが、Pd(210)表面のような特異的なステップ構造を有する表面では、解離吸着のほか、分子状化学吸着することが知られている。吸着水素分子のオルト-パラ転換を調べるために、今回新たに分子線, 光刺激脱離および共鳴多光子イオン化法を組み合わせた測定手法を確立した。本発表では、この実験手法を用いて測定したPd(210)表面でのH$$_{2}$$のオルト-パラ転換時間について報告する。

口頭

Pd(210)表面に化学吸着した水素分子のオルト-パラ転換時間測定

植田 寛和; 笹川 裕矢*; Ivanov, D.*; 大野 哲*; 小倉 正平*; 福谷 克之

no journal, , 

水素分子は、Pd(210)表面のように特有なステップ構造をもつ表面では、解離吸着のほか分子状化学吸着する。本研究では、分子線, 光刺激脱離および共鳴多光子イオン化法を用いて、Pd(210)表面に化学吸着した水素分子のオルト-パラ転換を調べた。決定された転換時間は過去に報告されている物理吸着系(数百-千秒)と比べて大変短い2秒程度であった。発表では、測定結果とともに速い転換の起源について議論する予定である。

口頭

パラジウムステップ表面に吸着した水素分子のオルトーパラ転換

植田 寛和; 笹川 裕矢*; Ivanov, D.*; 大野 哲*; 小倉 正平*; 福谷 克之

no journal, , 

表面温度50KでPd(210)表面に化学吸着した水素分子のオルト-パラ転換時間を測定した。実験の結果、転換時間は2秒程度であることが分かった。この時間は過去に2次摂動の転換モデルを基に見積もられた時間と同等であり、本研究はその転換モデルの正当性を支持する。

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