研究者データベース

香内 晃(コウウチ アキラ)
低温科学研究所 雪氷新領域部門
教授

基本情報

所属

  • 低温科学研究所 雪氷新領域部門

職名

  • 教授

学位

  • 理学博士

J-Global ID

研究キーワード

  • 惑星科学   Planetary Sciences   

研究分野

  • ナノテク・材料 / 結晶工学
  • ナノテク・材料 / 応用物性
  • 自然科学一般 / 固体地球科学
  • 自然科学一般 / 固体地球科学

学歴

  •         - 1981年   東北大学   理学研究科   地学
  •         - 1981年   東北大学
  •         - 1979年   東北大学   理学部   地学第2
  •         - 1979年   東北大学

所属学協会

  • 日本岩石鉱物鉱床学会   日本結晶成長学会   日本鉱物学会   日本雪氷学会   日本惑星科学会   

研究活動情報

論文

  • Takekoshi, Tatsuya, Ohtawara, Kazushige, Oshima, Tai, Ishii, Shun, Izumi, Natsuko, Izumi, Takuma, Yamaguchi, Masayuki, Suzuki, Shunta, Muraoka, Kazuyuki, Hirota, Akihiko, Saito, Fumiaki, Nakatsubo, Shunichi, Kouchi, Akira, Ito, Tetsuya, Uemizu, Kazunori, Fujii, Yasunori, Tamura, Yoichi, Kohno, Kotaro, Kawabe, Ryohei
    Journal of Low Temperature Physics 7pp  2018年12月 [査読有り][通常論文]
     
    We developed a simple add-on, cryogen-free, and low-power consumption calibrator for a new transition-edge sensor (TES) bolometer camera mounted on the ASTE 10-m telescope. To measure the responsivity of the TES bolometers and accurately correct for the nonlinearity and atmospheric extinction, we designed a motor-driven rotating filter wheel system installed in front of the cryostat window. This calibrator is required to cover the loading power under various atmospheric conditions, which corresponds to precipitable water vapor (PWV) of 0.5-4 mm. For this range of PWV, 25-100 K blackbodies are necessary for the observing bands of 1.1 and 0.85 mm. To simulate the temperature range, bolometers in the cryostat are also optically coupled to the low-temperature stage (<4 K) inside the cryostat by spherical mirrors. In addition, we used moderately absorptive polystyrene plates that are placed between a spherical mirror and the cryostat window. Various combinations of filters result in eight different temperatures by the filter wheel system and simulate the atmospheric emission under various weather conditions at the ASTE site.

    ...

  • Oshima, Tai, Ohtawara, Kazushige, Takekoshi, Tatsuya, Ishii, Shun, Izumi, Natsuko, Izumi, Takuma, Yamaguchi, Masayuki, Suzuki, Shunta, Muraoka, Kazuyuki, Hirota, Akihiko, Saito, Fumiaki, Nakatsubo, Shunichi, Kouchi, Akira, Ito, Tetsuya, Uemizu, Kazunori, Fujii, Yasunori, Tamura, Yoichi, Kohno, Kotaro, Kawabe, Ryohei
    Journal of Low Temperature Physics 2018年12月 [査読有り][通常論文]
     
    We developed and deployed a simple add-on multi-temperature calibrator for our multicolor transition edge sensor (TES) bolometer camera aimed at simultaneous observation with observing wavelengths of 1.1 and 0.85 mm. To cover the power loading level from the atmospheric emission corresponding to precipitable water vapor (PWV) of 0.5-4 mm, the calibrator consists of spherical mirrors to show the low-temperature stages of the cryostat and filters with moderate opacity to mimic the eight-temperature cold blackbodies. The loading powers introduced by each filter were self-calibrated by measuring the load curves of the TES bolometers when a filter was placed in front of the cryostat window. Each science observation was preceded by the calibration process, which measures the response of the TES bolometers to the atmosphere and filters of various opacities. Then, the responsivities of TES bolometers were derived to convert their output signal to the loading power and correct for the nonlinearity inherent in its response. Furthermore, the loading power falling on the TES bolometers from atmospheric emission measured at various PWV was in good correlation with the PWV measured with the radiometer, which enables the atmospheric extinction correction by fast and sensitive bolometers compared to the available radiometers with the modest sampling speeds.

    ...

  • Y. Kimura, M. Tsuge, V. Pirronello, A. Kouchi, N. Watanabe
    The Astrophysical Journal Letters 858 L23 5pp  2018年05月 [査読有り][通常論文]
  • T. Hama, A. Kouchi, N. Watanabe
    The Astrophysical Journal Letters 857 L13 6pp  2018年04月 [査読有り][通常論文]
  • Y. Oba, T. Tomaru, T. Lamberts, A. Kouchi, N. Watanabe
    Nature Astronomy 2 228 - 232 2018年02月 [査読有り][通常論文]
  • Tetsuya Hama, Akira Kouchi, Naoki Watanabe, Shinichi Enami, Takafumi Shimoaka, Takeshi Hasegawa
    JOURNAL OF PHYSICAL CHEMISTRY B 121 49 11124 - 11131 2017年12月 [査読有り][通常論文]
     
    The outermost surface of the leaves of land plants is covered with a lipid membrane called the cuticle that protects against various stress factors. Probing the molecular-level structure of the intact cuticle is highly desirable for understanding its multifunctional properties. We report the in situ characterization of the surface structure of Kalanchoe pinnata leaves using polarization-modulation infrared reflection absorption spectroscopy (PM-IRRAS). Without sample pretreatment, PM-IRRAS measures the IR spectra of the leaf cuticle of a potted K. pinnata plant. The peak position of the CH2-related modes shows that the cuticular waxes on the leaf surface are mainly crystalline, and the alkyl chains are highly packed in an all-trans zigzag conformation. The surface selection rule of PM-IRRAS revealed the average orientation of the cuticular molecules, as indicated by the positive and negative signals of the IR peaks. This unique property of PM-IRRAS revealed that the alkyl chains of the waxes and the main chains of polysaccharides are oriented almost perpendicular to the leaf surface. The nondestructive, background-free, and environmental gas-free nature of PM-IRRAS allows the structure and chemistry of the leaf cuticle to be studied directly in its native environment.
  • Yasuhiro Oba, Yoshinori Takano, Hiroshi Naraoka, Akira Kouchi, Naoki Watanabe
    ASTROPHYSICAL JOURNAL 849 2 9pp  2017年11月 [査読有り][通常論文]
     
    Hexamethylenetetramine (HMT) is a representative product after the photolysis of interstellar ice analogs containing methanol followed by warming-up to room temperature. Since interstellar methanol is often significantly enriched in deuterium (D), the HMT photoproduct is expected to inherit D atoms from deuterated methanol. However, D fractionation upon the formation of HMT is not well understood, especially when it is produced from partly deuterated methanol isotopologues such as CH2DOH and CH3OD. Here, we experimentally studied the composition of deuterated HMT (d(n)-HMT, where n is the number of D atoms) at the isotopologue level formed by the photolysis of ice mixtures containing deuterated methanol, CH2DOH or CH3OD, at 10 or 77 K. The analyses were performed using a state-of-the-art high-resolution mass spectrometer coupled with a compoundspecific separation technique. The formation of dn-HMT (n = 0-8) was confirmed under all experimental conditions. In addition, methyl-and hydroxyl-substituted HMT and their deuterated isotopologues were also obtained in the products. The deuterium enrichment was outstanding when CH2DOH was used rather than CH3OD, and when photolysis was performed at 77 K rather than 10 K. We found that the deuteration level of the formed HMT far exceeded that of the reactants under the present experimental conditions. These results obtained during stable isotope probing of deuterium strongly suggest that HMT can play a role as an organic pool of interstellar D atoms. These may be distributed into other chemical species through molecular evolution in space.
  • Shogo Tachibana, Akira Kouchi, Tetsuya Hama, Yasuhiro Oba, Laurette Piani, Iyo Sugawara, Yukiko Endo, Hiroshi Hidaka, Yuki Kimura, Ken-Ichiro Murata, Hisayoshi Yurimoto, Naoki Watanabe
    Science advances 3 9 eaao2538  2017年09月 [査読有り][通常論文]
     
    Interstellar ice is believed to be a cradle of complex organic compounds, commonly found within icy comets and interstellar clouds, in association with ultraviolet (UV) irradiation and subsequent warming. We found that UV-irradiated amorphous ices composed of H2O, CH3OH, and NH3 and of pure H2O behave like liquids over the temperature ranges of 65 to 150 kelvin and 50 to 140 kelvin, respectively. This low-viscosity liquid-like ice may enhance the formation of organic compounds including prebiotic molecules and the accretion of icy dust to form icy planetesimals under certain interstellar conditions.
  • T. Hama, S. Ishizuka, T. Yamazaki, Y. Kimura, A. Kouchi, N.Watanabe, T. Sugimoto, V. Pirronello
    Phys. Chem. Chem. Phys. 2017 19 17677 - 17684 2017年06月 [査読有り][通常論文]
  • Rafael Escribano, Emilio Artacho, Akira Kouchi, Tetusya Hama, Yuki Kimura, Hiroshi Hidaka, Naoki Watanabe
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS 19 10 7280 - 7287 2017年03月 [査読有り][通常論文]
     
    Models for the inclusion of water molecules in carbon monoxide matrices are developed using density functional theory applied to amorphous solid systems. The models cover a large range of systems for smaller or larger CO matrices with different water content, consisting of either individual H2O molecules or small clusters linked by H-bonds. The vibrational spectra of the samples are predicted at the minimum of their potential energy surface. The spectra allow instances where the water molecules remain isolated or form aggregates to be discerned, and they also provide an indication of the strength of the H-bonding, when present. The calculations support recent experimental observations that linked IR bands at 3707 cm(-1) and 3617 cm(-1) to the presence of unbound water molecules in water-poor CO/H2O mixed ices. Assignment of some observed bands to water dimers or trimers is suggested as well. The residual static pressure in fixed-volume simulation cells is also calculated.
  • L. Piani, S. Tachibana, T. Hama, H. Tanaka, Y. Endo, I. Sugawara, L. Dessimoulie, Y. Kimura, A. Miyake, J. Matsuno, A. Tsuchiyama, K. Fujita, S. Nakatsubo, H. Fukushi, S. Mori, T. Chigai, H. Yurimoto, A. Kouchi
    ASTROPHYSICAL JOURNAL 837 1 35 (11pp)  2017年03月 [査読有り][通常論文]
     
    Refractory organic compounds formed in molecular clouds are among the building blocks of the solar system objects and could be the precursors of organic matter found in primitive meteorites and cometary materials. However, little is known about the evolutionary pathways of molecular cloud organics from dense molecular clouds to planetary systems. In this study, we focus on the evolution of the morphological and viscoelastic properties of molecular cloud refractory organic matter. We found that the organic residue, experimentally synthesized at similar to 10 K from UV-irradiated H2O-CH3OH-NH3 ice, changed significantly in terms of its nanometer to micrometer-scale morphology and viscoelastic properties after UV irradiation at room temperature. The dose of this irradiation was equivalent to that experienced after short residence in diffuse clouds (<= 10(4) years) or irradiation in outer protoplanetary disks. The irradiated organic residues became highly porous and more rigid and formed amorphous nanospherules. These nanospherules are morphologically similar to organic nanoglobules observed in the least-altered chondrites, chondritic porous interplanetary dust particles, and cometary samples, suggesting that irradiation of refractory organics could be a possible formation pathway for such nanoglobules. The storage modulus (elasticity) of photo-irradiated organic residues is similar to 100 MPa irrespective of vibrational frequency, a value that is lower than the storage moduli of minerals and ice. Dust grains coated with such irradiated organics would therefore stick together efficiently, but growth to larger grains might be suppressed due to an increase in aggregate brittleness caused by the strong connections between grains.
  • 超高真空極低温透過型電子顕微鏡の開発─氷のその場観察をめざして─
    香内晃, 日高宏, 羽馬哲也, 木村勇気, 渡部直樹, 中坪俊一, 藤田和之, 新堀邦夫, 池田正幸
    雪氷 2017年 [査読有り][通常論文]
  • 星間塵表面における量子トンネル水素付加反応:その同位体効果と表面構造依存
    羽馬哲也, 渡部直樹, 香内晃
    触媒 59 5 242 - 248 2017年 [査読有り][通常論文]
  • 羽馬哲也, 香内晃, 渡部直樹
    化学と教育 64 282 - 283 2016年12月 [査読有り][通常論文]
  • Yasuhiro Oba, Naoki Watanabe, Akira Kouchi
    CHEMICAL PHYSICS LETTERS 662 14 - 18 2016年10月 [査読有り][通常論文]
     
    We report an experimental study on the catalytic effect of solid water on the reactivity of hydrogen abstraction (H-abstraction) from dimethyl ether (DME) in the low-temperature solid DME-H2O complex. When DME reacted with deuterium atoms on a surface at 15-25 K, it was efficiently deuterated via successive tunneling H-abstraction and deuterium (D)-addition reactions. The 'effective rate constant for DME-H2O + D was found to be about 20 times smaller than that of pure DME + D. This provides the first evidence that the presence of solid water has a negative catalytic effect on tunneling H-abstraction reactions. (C) 2016 Elsevier B.V. All rights reserved.
  • Yasuhiro Oba, Kazuya Osaka, Takeshi Chigai, Akira Kouchi, Naoki Watanabe
    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 462 1 689 - 695 2016年10月 [査読有り][通常論文]
     
    Ethanol (CH3CH2OH) is one of the most abundant complex organic molecules in star-forming regions. Despite its detection in the gas phase only, ethanol is believed to be formed by low temperature grain-surface reactions. Methanol, the simplest alcohol, has been a target for observational, experimental, and theoretical studies in view of its deuterium enrichment in the interstellar medium; however, the deuterium chemistry of ethanol has not yet been an area of focus. Recently, deuterated dimethyl ether, a structural isomer of ethanol, was found in star forming regions, indicating that deuterated ethanol can also be present in those environments. In this study, we performed laboratory experiments on the deuterium fractionation of solid ethanol at low temperatures through a reaction with deuterium (D) atoms at 10 K. Hydrogen (II)-D substitution, which increases the deuteration level, was found to occur on the ethyl group but not on the hydroxyl group. In addition, when deuterated ethanol (e.g. CD3CD2OD) solid was exposed to H atoms at 10 K, D-H substitution that reduced the deuteration level occurred on the ethyl group. Based on the results, it is likely that deuterated ethanol is present even under H-atom-dominant conditions in the interstellar medium.
  • Yasuhiro Oba, Yoshinori Takano, Naoki Watanabe, Akira Kouchi
    ASTROPHYSICAL JOURNAL LETTERS 827 1 L18 (7pp)  2016年08月 [査読有り][通常論文]
     
    Deuterium (D) atoms in interstellar deuterated methanol might be distributed into complex organic molecules through molecular evolution by photochemical reactions in interstellar grains. In this study, we use a state-of-the-art high-resolution mass spectrometer coupled with a high-performance liquid chromatography system to quantitatively analyze amino acids and their deuterated isotopologues formed by the photolysis of interstellar ice analogs containing singly deuterated methanol CH2DOH at 10 K. Five amino acids (glycine, alpha-alanine, beta-alanine, sarcosine, and serine) and their deuterated isotopologues whose D atoms are bound to carbon atoms are detected in organic residues formed by photolysis followed by warming up to room temperature. The abundances of singly deuterated amino acids are in the range of 0.3-1.1 relative to each nondeuterated counterpart, and the relative abundances of doubly and triply deuterated species decrease with an increasing number of D atoms in a molecule. The abundances of amino acids increase by a factor of more than five upon the hydrolysis of the organic residues, leading to decreases in the relative abundances of deuterated species for alpha-alanine and beta-alanine. On the other hand, the relative abundances of the deuterated isotopologues of the other three amino acids did not decrease upon hydrolysis, indicating different formation mechanisms of these two groups upon hydrolysis. The present study facilitates both qualitative and quantitative evaluations of D fractionation during molecular evolution in the interstellar medium.
  • A. Kouchi, T. Hama, Y. Kimura, H. Hidaka, R. Escribano, N. Watanabe
    CHEMICAL PHYSICS LETTERS 658 287 - 292 2016年08月 [査読有り][通常論文]
     
    A novel method for the formation of amorphous ice involving matrix sublimation has been developed. A CO-rich CO:H2O mixed ice was deposited at 8-10 K under ultra-high vacuum condition, which was then allowed to warm. After the sublimation of matrix CO at 35 K, amorphous ice remained. The amorphous ice formed exhibits a highly porous microscale texture; however, it also rather exhibits a density similar to that of high-density amorphous ice formed under high pressure. Furthermore, unlike conventional vapor-deposited amorphous ice, the amorphous ice is stable up to 140 K, where it transforms directly to cubic ice Ic. (C) 2016 Elsevier B.V. All rights reserved.
  • Hirokazu Ueta, Naoki Watanabe, Tetsuya Hama, Akira Kouchi
    PHYSICAL REVIEW LETTERS 116 25 253201  2016年06月 [査読有り][通常論文]
     
    The surface temperature dependence of the ortho-to-para conversion of H-2 on amorphous solid water is first reported. A combination of photostimulated desorption and resonance-enhanced multiphoton ionization techniques allowed us to sensitively probe the conversion on the surface of amorphous solid water at temperatures of 9.2-16 K. Within a narrow temperature window of 8 K, the conversion time steeply varied from similar to 4.1 x 10(3) to similar to 6.4 x 10(2) s. The observed temperature dependence is discussed in the context of previously suggested models and the energy dissipation process. The two-phonon process most likely dominates the conversion rate at low temperatures.
  • 羽馬哲也, 植田寛和, 渡部直樹, 香内晃
    地球化学 50 2 33 - 50 2016年06月 [査読有り][通常論文]
  • Tetsuya Hama, Akira Kouchi, Naoki Watanabe
    SCIENCE 351 6268 65 - 67 2016年01月 [査読有り][通常論文]
     
    The anomalously low ortho-to-para ratios (OPRs) exhibited by gaseous water in space have been used to determine the formation temperature (<50 kelvin) of ice on cold interstellar dust. This approach assumes that the OPR of water desorbed from ice is related to the ice formation temperature on the dust. However, we report that water desorbed from ice at 10 kelvin shows a statistical high-temperatureOPRof 3, even when the ice is produced in situ by hydrogenation of O-2, a known formation process of interstellar water. This invalidates the assumed relation between OPR and temperature. The necessary reinterpretation of the low OPRs will help elucidate the chemical history of interstellar water from molecular clouds and processes in the early solar system, including comet formation.
  • K. Kuwahata, T. Hama, A. Kouchi, N. Watanabe
    PHYSICAL REVIEW LETTERS 115 13 133201  2015年09月 [査読有り][通常論文]
     
    Reported here is the first observation of the tunneling surface diffusion of a hydrogen (H) atom on water ice. Photostimulated desorption and resonance-enhanced multiphoton ionization methods were used to determine the diffusion rates at 10 Kon amorphous solid water and polycrystalline ice. H-atom diffusion on polycrystalline ice was 2 orders of magnitude faster than that of deuterium atoms, indicating the occurrence of tunneling diffusion. Whether diffusion is by tunneling or thermal hopping also depends on the diffusion length of the atoms and the morphology of the surface. Our findings contribute to a better understanding of elementary physicochemical processes of hydrogen on cosmic ice dust.
  • 羽馬哲也, 香内晃, 渡部直樹
    日本物理学会誌 70 8 608 - 613 2015年08月 [査読有り][通常論文]
  • Y. Oba, N. Watanabe, Y. Osamura, A.Kouchi
    Chem. Phys. Lett. 634 53 - 59 2015年08月 [査読有り][通常論文]
     
    We report experimental evidence that chiral glycine (NH2CHDCOOH) is formed by the surface reaction of normal glycine (NH2CH2COOH) solid with deuterium (D) atom at 12K under the simulative conditions of interstellar molecular clouds. Chiral glycine formation is most likely initiated by the tunneling abstraction reaction of H atom by D atom followed by the addition of D atom to the glycine radical (NH2CHCOOH). Given that chiral glycine can form in such a primordial low-temperature environment, it might source molecular chirality as molecular clouds evolve into planetary systems. (C) 2015 Elsevier B.V. All rights reserved.
  • S. K. Simakov, A. Kouchi, N. N. Mel'nik, V. Scribano, Y. Kimura, T. Hama, N. Suzuki, H. Saito, T. Yoshizawa
    SCIENTIFIC REPORTS 5 10765  2015年06月 [査読有り][通常論文]
     
    Most of Earth's diamonds are connected with deep-seated mantle rocks; however, in recent years, mu m-sized diamonds have been found in shallower metamorphic rocks, and the process of shallow-seated diamond formation has become a hotly debated topic. Nanodiamonds occur mainly in chondrite meteorites associated with organic matter and water. They can be synthesized in the stability field of graphite from organic compounds under hydrothermal conditions. Similar physicochemical conditions occur in serpentinite-hosted hydrothermal systems. Herein, we report the first finding of nanodiamonds, primarily of 6 and 10 nm, in Hyblean asphaltene-bearing serpentinite xenoliths (Sicily, Italy). The discovery was made by electron microscopy observations coupled with Raman spectroscopy analyses. The finding reveals new aspects of carbon speciation and diamond formation in shallow crustal settings. Nanodiamonds can grow during the hydrothermal alteration of ultramafic rocks, as well as during the lithogenesis of sediments bearing organic matter.
  • Tetsuya Hama, Hirokazu Ueta, Akira Kouchi, Naoki Watanabe
    PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA 112 24 7438 - 7443 2015年06月 [査読有り][通常論文]
     
    Classical transition-state theory is fundamental to describing chemical kinetics; however, quantum tunneling is also important in explaining the unexpectedly large reaction efficiencies observed in many chemical systems. Tunneling is often indicated by anomalously large kinetic isotope effects (KIEs), because a particle's ability to tunnel decreases significantly with its increasing mass. Here we experimentally demonstrate that cold hydrogen (H) and deuterium (D) atoms can add to solid benzene by tunneling; however, the observed H/D KIE was very small (1-1.5) despite the large intrinsic H/D KIE of tunneling (greater than or similar to 100). This strong reduction is due to the chemical kinetics being controlled not by tunneling but by the surface diffusion of the H/D atoms, a process not greatly affected by the isotope type. Because tunneling need not be accompanied by a large KIE in surface and interfacial chemical systems, it might be overlooked in other systems such as aerosols or enzymes. Our results suggest that surface tunneling reactions on interstellar dust may contribute to the deuteration of interstellar aromatic and aliphatic hydrocarbons, which could represent a major source of the deuterium enrichment observed in carbonaceous meteorites and interplanetary dust particles. These findings could improve our understanding of interstellar physicochemical processes, including those during the formation of the solar system.
  • Tetsuya Hama, Hirokazu Ueta, Akira Kouchi, Naoki Watanabe, Hiroto Tachikawa
    JOURNAL OF PHYSICAL CHEMISTRY LETTERS 5 21 3843 - 3848 2014年11月 [査読有り][通常論文]
     
    Despite the rapid accumulation of structural information about organic materials, the correlation between the surface structure of these materials and their chemical properties, a potentially important aspect of their chemistry, is not fully understood. Here, we show that the amorphous or crystalline structure of a solid benzene surface controls its chemical reactivity toward hydrogen. In situ infrared spectroscopy revealed that cold hydrogen atoms can add to an amorphous benzene surface at 20 K to form cyclohexane by tunneling. However, hydrogenation is greatly reduced on crystalline benzene. We suggest that the origin of the high selectivity of this reaction is the large difference in geometric constraints between the amorphous and the crystalline surfaces. The present findings can lead us to a more complete understanding of heterogeneous reaction systems, especially those involving tunneling, as well as to the possibility of nonenergetic surface chemical modification without undesired side reactions or physical processes.
  • Yasuhiro Oba, Kazuya Osaka, Naoki Watanabe, Takeshi Chigai, Akira Kouchi
    FARADAY DISCUSSIONS 168 185 - 204 2014年08月 [査読有り][通常論文]
     
    We performed laboratory experiments on the formation of water and its isotopologues by surface reactions of hydrogen peroxide (H2O2) with hydrogen (H) atoms and their deuterated counterparts (D2O2, D) at 10-30 K. High-purity H2O2 (>95%) was prepared in situ by the codeposition of molecular oxygen and H atoms at relatively high temperatures (45-50 K). We determined that the high-purity H2O2 solid reacts with both H and deuterium (D) atoms at 10-30 K despite the large activation barriers (similar to 2000 K). Moreover, the reaction rate for H atoms is approximately 45 times faster than that for D atoms at 15 K. Thus, the observed large isotope effect indicates that these reactions occurred through quantum tunneling. We propose that the observed HDO/H2O ratio in molecular clouds might be a good tool for the estimation of the atomic D/H ratio in those environments.
  • Yasuhiro Oba, Takeshi Chigai, Yoshihiro Osamura, Naoki Watanabe, Akira Kouchi
    METEORITICS & PLANETARY SCIENCE 49 1 117 - 132 2014年01月 [査読有り][通常論文]
     
    We experimentally studied hydrogen (H)-deuterium (D) substitution reactions of solid methylamine (CH3NH2) under astrophysically relevant conditions. We also calculated the potential energy surface for the H-D substitution reactions of methylamine isotopologues using quantum chemical methods. Despite the relatively large energy barrier of more than 18kJmol(-1), CH3NH2 reacted with D atoms to yield deuterated methylamines at 10K, suggesting that the H-D substitution reaction proceeds through quantum tunneling. Deuterated methylamines reacted with H atoms as well. On the basis of present results, we propose that methylamine has potential for D enrichment through atomic surface reactions on interstellar grains at very low temperatures in molecular clouds. D enrichment would occur in particular in the methyl group of methylamine.
  • Naoki Watanabe, Tetsuya Hama, Akira Kouchi
    FIRST INTERNATIONAL CONFERENCE ON CHEMICAL EVOLUTION OF STAR FORMING REGION AND ORIGIN OF LIFE (ASTROCHEM2012) 1543 308 - 316 2013年 [査読有り][招待有り]
     
    To clarify the meaning of the nuclear spin temperatures of H-2 and H2O molecules associated with various astronomical targets, it is important to understand the mechanisms that could alter these temperatures; i.e., the molecules' ortho/para nuclear-spin ratio (OPR). We have performed a series of experiments to investigate how the OPRs of H-2 and H2O behave on the surface of amorphous solid water (ASW), which is analogous to cosmic ice dust. The OPR of H-2 initially shows a high temperature limit of 3 upon its formation through H-H recombination at similar to 10 K and gradually decreases toward lower temperatures on the surface. The spin temperatures of H2O molecules that are thermally desorbed from various types of ASW at similar to 10 K always return the high-temperature limit.
  • N. Watanabe, T. Hama, A. Kouchi
    AIP Conference Proceedings 1543 308 - 316 2013年 [査読有り][招待有り]
  • Tetsuya Hama, Kazuaki Kuwahata, Naoki Watanabe, Akira Kouchi, Yuki Kimura, Takeshi Chigai, Valerio Pirronello
    ASTROPHYSICAL JOURNAL 757 2 185  2012年10月 [査読有り][通常論文]
     
    To understand elementary processes leading to H-2 formation, and the hydrogenation and deuteration reactions of adsorbed species on dust grains in dense clouds, we experimentally investigated the diffusion of atomic hydrogen and deuterium on amorphous solidwater (ASW) at temperatures of 8-15 K. The present study extended our previous study for selective detections of H and D atoms, and of H-2 (J = 0 and 1) and D-2 (J = 0 and 1) molecules adsorbed on ASW using both photo-stimulated desorption and resonance-enhanced multiphoton ionization, to investigate potential sites on ASW for diffusion, recombination dynamics, and the diffusion mechanism of H and D atoms. Our results demonstrate that the ASW surface contains various potential sites that can be categorized into at least three groups: very shallow, middle-, and deep-potential sites, with diffusion activation energies of <= 18, 22 (23 meV for D atoms), and >= 30 meV, respectively. The present study pictured the outline of H-2 formation on cosmic ice dust at low temperatures: H atoms landing on the dust will diffuse rapidly at the abundant shallow and middle sites on ASW, and finally become trapped at deep sites. The H atoms that arrive next recombine with such trapped H atoms to yield H-2 molecules. The small isotopic difference between the diffusion of H and D atoms on ASW indicates that the diffusion mechanism can be explained by thermal hopping, at least at middle-potential sites.
  • T. Hama, K. Kuwahata, N. Watanabe, A. Kouchi, Y. Kimura, T. Chigai, V. Pirronello
    Astrophys. J. 757 2 185  2012年09月 [査読有り][通常論文]
  • Y. Oba, N. Watanabe, T. Hama, K. Kuwahata, H. Hidaka, A. Kouchi
    ASTROPHYSICAL JOURNAL 749 1 67  2012年04月 [査読有り][通常論文]
     
    The present study experimentally demonstrated that solid H2O is formed through the surface reaction OH + H-2 at 10 K. This is the first experimental evidence of solid H2O formation using hydrogen in its molecular form at temperatures as low as 10 K. We further found that H2O formation through the reaction OH + H-2 is about one order of magnitude more effective than HDO formation through the reaction OH + D-2. This significant isotope effect results from differences in the effective mass of each reaction, indicating that the reactions proceed through quantum tunneling.
  • Y. Oba, N. Watanabe, T. Hama, K. Kuwahata, H. Hidaka, A. Kouchi
    ASTROPHYSICAL JOURNAL 749 1 67  2012年04月 [査読有り][通常論文]
     
    The present study experimentally demonstrated that solid H2O is formed through the surface reaction OH + H-2 at 10 K. This is the first experimental evidence of solid H2O formation using hydrogen in its molecular form at temperatures as low as 10 K. We further found that H2O formation through the reaction OH + H-2 is about one order of magnitude more effective than HDO formation through the reaction OH + D-2. This significant isotope effect results from differences in the effective mass of each reaction, indicating that the reactions proceed through quantum tunneling.
  • 渡部直樹, 香内晃, 羽馬哲也, 日高宏, 大場康弘, 千貝健
    表面科学 33 12 662 - 668 2012年 [査読有り][通常論文]
  • T. Hama, N. Watanabe, A. Kouchi, M. Yokoyama
    ASTROPHYSICAL JOURNAL LETTERS 738 1 2011年09月 [査読有り][通常論文]
     
    The nuclear-spin temperature of molecules observed in interstellar space or cometary coma is an important key to understanding physical and chemical histories of the molecules. The present Letter reports measurements of nuclear-spin states and rotational temperatures of thermally desorbed H2O molecules from amorphous solid water (ASW) by combining temperature-programmed desorption and resonance-enhanced multiphoton ionization (REMPI). REMPI spectra of desorbed H2O molecules were measured at similar to 150 K from vapor-deposited ASW at 8 K. The nuclear-spin temperature of desorbed H2O molecules exhibits almost an upper limit to the ortho-to-para ratio of close to 3. No discernible change was observed in the H2O REMPI spectrum, neither after leaving the deposited ASW for 9 days in a vacuum chamber at 8 K, nor in the presence of O-2 molecules, nor upon exposure of ASW to vacuum-ultraviolet (VUV) photons. Desorbed H2O molecules were also investigated from ASW produced by VUV irradiation of a CH4/O-2 mixture at 8 K. The resulting H2O spectrum showed a high nuclear-spin temperature. These results suggest that the nuclear-spin temperatures of gaseous H2O molecules thermally desorbed from ice do not necessarily reflect the surface temperature at which H2O molecules condensed or formed under some laboratory conditions. We discuss the possibility of nuclear-spin conversion of H2O in water ice. The present study advocates the importance of further studies to give an interpretation of nuclear-spin temperatures of molecules observed in interstellar space or cometary coma.
  • T. Hama, N. Watanabe, A. Kouchi, M. Yokoyama
    Astrophys. J. Lett. 738 1 2011年08月 [査読有り][通常論文]
  • Y. Oba, N. Watanabe, A. Kouchi, T. Hama, V. Pirronello
    Phys. Chem. Chem. Phys. 13 35 15792 - 15797 2011年07月 [査読有り][通常論文]
  • Hiroshi Hidaka, Motohiro Watanabe, Akira Kouchi, Naoki Watanabe
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS 13 35 15798 - 15802 2011年 [査読有り][通常論文]
     
    A Fourier transform infrared absorption spectroscopy (FTIR) study showed that NH3 was formed by the successive reaction of hydrogen atoms with nitrogen atoms in an N-2 matrix at 10 K. Reactions appeared to proceed via the Langmuir-Hinshelwood mechanism because NH3 formation was not observed at 20 K. At this temperature, H atoms did not adsorb significantly onto the N-2 matrix; i.e., the surface residence times were short. Furthermore, NH3 yields via the successive hydrogenation of N atoms were significant, even after H atom deposition onto the N-2 matrix containing trapped N atoms onto which had been deposited a superficial pure solid N-2 adlayer. This result clearly indicates that H atoms diffuse in pure solid N-2 matrices at 10 K.
  • 大場 康弘, 渡部 直樹, 香内 晃, 羽馬 哲也, ピロネロ バレリオ
    地球化学 45 4 213 - 226 2011年 [査読有り][通常論文]
  • Yasuhiro Oba, Naoki Watanabe, Akira Kouchi, Tetsuya Hama, Valerio Pirronello
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS 13 35 15792 - 15797 2011年 [査読有り][通常論文]
     
    We investigated the OH-related formation routes of two astrophysically important molecules, H2O and CO2, under relatively warm astrophysical conditions. OH radicals, together with other neutral species such as H, O, H-2, and O-2, were produced in H2O microwave-discharge plasma and cooled to 100 K before being deposited on an Al substrate at 40-60 K. H2O formed at 40 and 50 K, but not at 60 K. Taking the experimental conditions into account, a possible route of H2O formation is via reactions involving OH + OH, which yield H2O2 as the main reaction product. The present study is the first to show experimentally that surface reactions of two OH radicals can yield H2O at low temperatures. The products' branching ratio was 0.2 and 0.8 for H2O and H2O2, respectively. When CO was co-deposited with neutral species that formed in the H2O plasma, CO2 was formed at 40-60 K. H2CO3 formed at 40 and 50 K. The present results may suggest that chemical reactions related to OH radicals are effective at yielding various molecules in relatively warm astrophysical environments, such as protostars.
  • Hiroshi Hidaka, Motohiro Watanabe, Akira Kouchi, Naoki Watanabe
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS 13 35 15798 - 15802 2011年 [査読有り][通常論文]
     
    A Fourier transform infrared absorption spectroscopy (FTIR) study showed that NH3 was formed by the successive reaction of hydrogen atoms with nitrogen atoms in an N-2 matrix at 10 K. Reactions appeared to proceed via the Langmuir-Hinshelwood mechanism because NH3 formation was not observed at 20 K. At this temperature, H atoms did not adsorb significantly onto the N-2 matrix; i.e., the surface residence times were short. Furthermore, NH3 yields via the successive hydrogenation of N atoms were significant, even after H atom deposition onto the N-2 matrix containing trapped N atoms onto which had been deposited a superficial pure solid N-2 adlayer. This result clearly indicates that H atoms diffuse in pure solid N-2 matrices at 10 K.
  • Y. Oba, N. Watanabe, A. Kouchi, V. Pirronello
    Astrophys. J. 722 2,Pt.1 1598 - 1606 2010年10月 [査読有り][通常論文]
  • Y. Oba, N. Watanabe, A. Kouchi, V. Pirronello
    Astrophys. J. 722 2,Pt.1 1598 - 1606 2010年10月 [査読有り][通常論文]
  • Eui-Seong Moon, Heon Kang, Yasuhiro Oba, Naoki Watanabe, Akira Kouchi
    ASTROPHYSICAL JOURNAL 713 2 906 - 911 2010年04月 [査読有り][通常論文]
     
    We present direct evidence for ammonium ion (NH4+) formation through ultraviolet (UV) photolysis of NH3-H2O mixture ice that does not contain acids. NH4+ forms by the reaction of NH3 with protonic defects (H3O+) in the UV-photolyzed ice. Our observations may explain the deficient counter-anions in interstellar ice relative to the abundance of NH4+. Also, H3O+ may play an important role in the acid-base chemistry of interstellar ice in UV-irradiating environments. IR absorption results suggest that NH4+ is a potential contributor to the interstellar 6.85 mu m band but is not a dominant component.
  • N. Watanabe, Y. Kimura, A. Kouchi, T. Chigai, T. Hama, P. Valerio
    Astrophys. J. Lett. 714 2,Pt.2 L233 - L237 2010年04月 [査読有り][通常論文]
  • Y. Oba, N. Watanabe, A. Kouchi, T. Hama, V. Pirronello
    Astrophys. J. Lett. 712 2,Pt.2 L174 - L178 2010年03月 [査読有り][通常論文]
  • E.-S. Moon, H. Kang, Y. Oba, N. Watanabe, A. Kouchi
    Astrophys. J. 713 2,Pt.1 906 - 911 2010年03月 [査読有り][通常論文]
  • Y. Oba, N. Watanabe, A. Kouchi, T. Hama, V. Pirronello
    Astrophys. J. Lett. 712 2,Pt.2 L174 - L178 2010年03月 [査読有り][通常論文]
  • A. Kouchi, N. Watanabe, H. Hidaka, N. Miyauchi, Y. Oba, T. Chigai
    Astron. Soc. Pacific Conf. Ser. 414 338 - 346 2010年 [査読有り][通常論文]
  • N. Watanabe, Y. Kimura, A. Kouchi, T. Chigai, T. Hama, P. Valerio
    Astrophys. J. Lett. 714 2,Pt.2 L233 - L237 2010年 [査読有り][通常論文]
  • A. Kouchi, N. Watanabe, H. Hidaka, N. Miyauchi, Y. Oba, T. Chigai
    Astron. Soc. Pacific Conf. Ser. 414 338 - 346 2010年 [査読有り][通常論文]
  • H. Hidaka, M. Watanabe, A. Kouchi, N. Watanabe
    J. Phys. Conf. Ser. 194 132024  2009年12月 [査読無し][通常論文]
  • H. Hidaka, M. Watanabe, A. Kouchi, N. Watanabe
    J. Phys. Conf. Ser. 194 132024  2009年12月 [査読無し][通常論文]
  • H. Hidaka, M. Watanabe, A. Kouchi, N. Watanabe
    ASTROPHYSICAL JOURNAL 702 1 291 - 300 2009年09月 [査読有り][通常論文]
     
    Grain surface reaction has been expected to be a key process for deuterium enrichment in interstellar molecules. We focus on formaldehyde, which is predicted to be formed on cold grain surface in astrophysical models and is known to be deuterium-enriched in a molecular cloud. Reaction routes and effective reaction rate constants are experimentally investigated when H2CO and D2CO are exposed to D and H atoms on amorphous solid water (ASW) at 10-20 K, respectively. For D + H2CO on ASW, H2CO was converted to HDCO and D2CO by the H-D substitution reactions. Although CD3OD was slightly observed, doubly and triply deuterated methanol, CH2DOD and CHD2OD, were not observed. This implies that D addition to H2CO (formation of deuterated methanol) is a minor reaction route. On the other hand, for H + D2CO, H addition reactions to form CHD2OH proceed at a significant rate. Simultaneously, a competitive reaction, the substitution reaction by H atoms and subsequent H addition (D2CO -> HDCO -> H2CO -> CH3OH) also proceed at a significant rate. However, no H addition to HDCO was observed. The effective surface reaction routes when CO is exposed to H and D atoms are summarized using the present experimental results and the previous results of our group.
  • H. Hidaka, M. Watanabe, A. Kouchi, N. Watanabe
    Astrophys. J. 702 291 - 300 2009年08月 [査読有り][通常論文]
  • Y. Oba, N. Miyauchi, H. Hidaka, T. Chigai, N. Watanabe, A. Kouchi
    Astrophys. J. 701 1 464 - 470 2009年08月 [査読有り][通常論文]
  • Y. Oba, N. Miyauchi, H. Hidaka, T. Chigai, N. Watanabe, A. Kouchi
    Astrophys. J. 701 1 464 - 470 2009年07月 [査読有り][通常論文]
  • M. Goto, Th. Henning, A. Kouchi, H. Takami, Y. Hayano, T. Usuda, N. Takato, H. Terada, S. Oya, C. Jaeger, A. C. Andersen
    ASTROPHYSICAL JOURNAL 693 1 610 - 616 2009年03月 [査読無し][通常論文]
     
    We present spatially resolved 3 mu m spectra of Elias 1 obtained with an adaptive optics system. The central part of the disk is almost devoid of polycyclic aromatic hydrocarbon (PAH) emission at 3.3 mu m; it shows up only at 30 AU and beyond. The PAH emission extends up to 100 AU, at least to the outer boundary of our observation. The diamond emission, in contrast, is more centrally concentrated, with the column density peaked around 30 AU from the star. There are only three Herbig Ae/Be stars known to date that show diamond emission at 3.53 mu m. Two of them have low-mass companions likely responsible for the large X-ray flares observed toward the Herbig Ae/Be stars. We speculate on the origin of diamonds in circumstellar disks in terms of the graphitic material being transformed into diamond under the irradiation of highly energetic particles.
  • M. Goto, Th. Henning, A. Kouchi, H. Takami, Y. Hayano, T. Usuda, N. Takato, H. Terada, S. Oya, C. J ̈ager, A. C. Andersen
    Astrophys. J. 693 1 610 - 616 2009年03月 [査読無し][通常論文]
     
    We present spatially resolved 3 mu m spectra of Elias 1 obtained with an adaptive optics system. The central part of the disk is almost devoid of polycyclic aromatic hydrocarbon (PAH) emission at 3.3 mu m; it shows up only at 30 AU and beyond. The PAH emission extends up to 100 AU, at least to the outer boundary of our observation. The diamond emission, in contrast, is more centrally concentrated, with the column density peaked around 30 AU from the star. There are only three Herbig Ae/Be stars known to date that show diamond emission at 3.53 mu m. Two of them have low-mass companions likely responsible for the large X-ray flares observed toward the Herbig Ae/Be stars. We speculate on the origin of diamonds in circumstellar disks in terms of the graphitic material being transformed into diamond under the irradiation of highly energetic particles.
  • N. Watanabe, A. Kouchi, H. Hidaka, Y. Oba, N. Miyauchi
    XXVI INTERNATIONAL CONFERENCE ON PHOTONIC, ELECTRONIC AND ATOMIC COLLISIONS 194 012044  2009年 [査読有り][通常論文]
     
    Reactions of atomic hydrogen with CO and O-2 on amorphous solid water (ASW), relevant to chemical evolution on cosmic ice dust, were experimentally investigated at around 10 K. Successive addition of hydrogen atoms to CO and O-2 produces H2CO, CH3OH, and H2O2, H2O, respectively. At such low temperatures, some of hydrogen additions such as H + CO -> HCO proceed via tunneling reactions rather than thermally-activated reactions. Effective reaction rates and isotope effect of the tunneling reactions to produce HCO and H2O were measured. The surface of ASW was found to enhance the effective rate of hydrogen addition to CO at relatively higher temperatures, namely around 20 K.
  • 宇宙雪氷に関する研究の進展
    香内 晃
    「雪氷研究の系譜」日本雪氷学会北海道支部編 85 - 86 2009年 [査読有り][通常論文]
  • N. Watanabe, A. Kouchi, H. Hidaka, Y. Oba, N. Miyauchi
    XXVI INTERNATIONAL CONFERENCE ON PHOTONIC, ELECTRONIC AND ATOMIC COLLISIONS 194 12044  2009年 [査読有り][通常論文]
     
    Reactions of atomic hydrogen with CO and O-2 on amorphous solid water (ASW), relevant to chemical evolution on cosmic ice dust, were experimentally investigated at around 10 K. Successive addition of hydrogen atoms to CO and O-2 produces H2CO, CH3OH, and H2O2, H2O, respectively. At such low temperatures, some of hydrogen additions such as H + CO -> HCO proceed via tunneling reactions rather than thermally-activated reactions. Effective reaction rates and isotope effect of the tunneling reactions to produce HCO and H2O were measured. The surface of ASW was found to enhance the effective rate of hydrogen addition to CO at relatively higher temperatures, namely around 20 K.
  • Naoki Watanabe, Akira Kouchi
    PROGRESS IN SURFACE SCIENCE 83 10-12 439 - 489 2008年12月 [査読有り][通常論文]
     
    Chemical reactions on the surface of cosmic ice dust play an important role in chemical evolution in space. Arnong the many kinds of molecules observed, the abundances of some major species such as hydrogen molecules cannot be explained by gas-phase synthesis; therefore, surface reactions oil cosmic dust are considered for the synthesis of such molecules. Experimental research on surface reactions relevant to cosmic ice dust has been conducted since the late 1980s. Early experiments were rather qualitative, and so the details of reactions were not clear. In the last decade, many scientists from various fields including surface science have been motivated to extend the knowledge in this area of research, and have performed sophisticated experiments regarding surface reactions on cosmic ice dust. The aim of this article is to review the recent progress in surface astrochemistry. In particular, focus is made on experiments concerning the synthesis of abundant molecules such as H-2, H2O, CO2, H2CO and CH3OH oil ice surfaces at very low temperatures. (C) 2008 Elsevier Ltd. All rights reserved.
  • N. Watanabe, A. Kouchi
    Prog. Surf. Sci. 83 10-12 439 - 489 2008年12月 [査読有り][通常論文]
  • Toshihiko Kadono, Masahiko Arakawa, Akira Kouchi
    ICARUS 197 2 621 - 626 2008年10月 [査読無し][通常論文]
     
    We present the results of an aerodynamic liquid dispersion experiment using initially molten silicate samples. We investigate the threshold of breakup and the size distribution of dispersed droplets. The breakup threshold is consistent with the previous experiments using water and a mixture of water and glycerol. Also, we confirm the previous results that the size distributions of dispersed droplets are represented by an exponential form and that the characteristic size of dispersed droplets is related to the dynamic pressure of high-velocity gas flow. The size distribution has a similar form to that of chondrules, though the experiment is not exactly corresponding to the shock heating models for chondrule formation that consider solid precursors which are molten by the shocks. The experimental results indicate that, if liquid chondrule-precursors were dispersed by high-velocity flow, the dynamic pressure of the flow is similar to 10 kPa. A chondrule formation condition in a shock-wave heating model suggests that this pressure can be realized at the regions within similar to 1 AU in the minimum solar-nebula mass models. However, if the nebula had a larger mass and gravitational instabilities occurred, this pressure may be realized in the spiral arms at 2-3 AU and chondrules may be formed in asteroid belt. (C) 2008 Elsevier Inc. All rights reserved.
  • Toshihiko Kadono, Masahiko Arakawa, Akira Kouchi
    ICARUS 197 2 621 - 626 2008年10月 [査読無し][通常論文]
     
    We present the results of an aerodynamic liquid dispersion experiment using initially molten silicate samples. We investigate the threshold of breakup and the size distribution of dispersed droplets. The breakup threshold is consistent with the previous experiments using water and a mixture of water and glycerol. Also, we confirm the previous results that the size distributions of dispersed droplets are represented by an exponential form and that the characteristic size of dispersed droplets is related to the dynamic pressure of high-velocity gas flow. The size distribution has a similar form to that of chondrules, though the experiment is not exactly corresponding to the shock heating models for chondrule formation that consider solid precursors which are molten by the shocks. The experimental results indicate that, if liquid chondrule-precursors were dispersed by high-velocity flow, the dynamic pressure of the flow is similar to 10 kPa. A chondrule formation condition in a shock-wave heating model suggests that this pressure can be realized at the regions within similar to 1 AU in the minimum solar-nebula mass models. However, if the nebula had a larger mass and gravitational instabilities occurred, this pressure may be realized in the spiral arms at 2-3 AU and chondrules may be formed in asteroid belt. (C) 2008 Elsevier Inc. All rights reserved.
  • H. Hidaka, N. Miyauchi, A. Kouchi, N. Watanabe
    CHEMICAL PHYSICS LETTERS 456 1-3 36 - 40 2008年04月 [査読有り][通常論文]
     
    Experiments on the hydrogenation of CO on crystalline and amorphous ice at 15 K were carried out to investigate the structural effects of the ice surface. The effective rate of H atom addition to CO on the amorphous ice was found to be larger than that on the crystalline ice, while CO depletion on crystalline ice became larger after long exposure. We demonstrated that the CO-coverage on the ice surfaces dominates the effective reaction rate rather than the surface structure. The larger depletion of CO on crystalline ice, as compared to amorphous ice, suggests easier desorption of CO and/or products by the heat of the reaction. (C) 2008 Elsevier B.V. All rights reserved.
  • N. Miyauchi, H. Hidaka, T. Chigai, A. Nagaoka, N. Watanabe, A. Kouchi
    CHEMICAL PHYSICS LETTERS 456 1-3 27 - 30 2008年04月 [査読有り][通常論文]
     
    The reactions of cold H atoms with solid O-2 molecules were investigated at 10 K. The formation of H2O2 and H2O has been confirmed by in situ infrared spectroscopy. We found that the reaction proceeds very efficiently and obtained the effective reaction rates. This is the first clear experimental evidence of the formation of water molecules under conditions mimicking those found in cold interstellar molecular clouds. Based on the experimental results, we discuss the reaction mechanism and astrophysical implications. (C) 2008 Elsevier B.V. All rights reserved.
  • N. Miyauchi, H. Hidaka, T. Chigai, A. Nagaoka, N. Watanabe, A. Kouchi
    CHEMICAL PHYSICS LETTERS 456 1-3 27 - 30 2008年04月 [査読有り][通常論文]
     
    The reactions of cold H atoms with solid O-2 molecules were investigated at 10 K. The formation of H2O2 and H2O has been confirmed by in situ infrared spectroscopy. We found that the reaction proceeds very efficiently and obtained the effective reaction rates. This is the first clear experimental evidence of the formation of water molecules under conditions mimicking those found in cold interstellar molecular clouds. Based on the experimental results, we discuss the reaction mechanism and astrophysical implications. (C) 2008 Elsevier B.V. All rights reserved.
  • H. Hidaka, N. Miyauchi, A. Kouchi, N. Watanabe
    Chem. Phys. Lett. 456 1-3 36 - 40 2008年04月 [査読有り][通常論文]
  • N. Watanabe, O. Mouri, A. Nagaoka, T. Chigai, A. Kouchi
    Astrophys. J. 668 1001 - 1011 2007年10月 [査読有り][通常論文]
  • N. Watanabe, O. Mouri, A. Nagaoka, T. Chigai, A. Kouchi
    Astrophys. J. 668 1001 - 1011 2007年10月 [査読有り][通常論文]
  • H. Hidaka, A. Kouchi, N. Watanabe
    JOURNAL OF CHEMICAL PHYSICS 126 20 204707  2007年05月 [査読有り][通常論文]
     
    An experiment on the addition reaction of a D atom (deuteration) to CO on a cold ice surface is performed by deuterium atom exposure of three types of samples (pure solid CO, CO-capped H2O ice, and CO-H2O mixed ice) at 10-20 K. The variation of IR absorption spectra for the samples was measured by a Fourier transform infrared spectrometer during exposure to deuterium atoms. Reactions on pure solid CO were observed only at 10 K, while reactions on CO-capped H2O ice and CO-H2O mixed ice were observed to proceed even at 20 K. This indicates that the coexistence of H2O at the surface raises the reactive temperature. In addition, the experiment on H atom exposure was also carried out at 15 K to compare the reaction rate constant between the H and D atoms. The ratio of reaction rate constant k(D)/k(H) obtained is about 0.08 at 15 K. The authors provide information on the potential energy for the H+CO reaction at the surface by using the ratio k(D)/k(H) and by a model calculation of the potential tunneling with the asymmetric Eckart potential. (C) 2007 American Institute of Physics.
  • H. Hidaka, A. Kouchi, N. Watanabe
    JOURNAL OF CHEMICAL PHYSICS 126 20 204707  2007年05月 [査読有り][通常論文]
     
    An experiment on the addition reaction of a D atom (deuteration) to CO on a cold ice surface is performed by deuterium atom exposure of three types of samples (pure solid CO, CO-capped H2O ice, and CO-H2O mixed ice) at 10-20 K. The variation of IR absorption spectra for the samples was measured by a Fourier transform infrared spectrometer during exposure to deuterium atoms. Reactions on pure solid CO were observed only at 10 K, while reactions on CO-capped H2O ice and CO-H2O mixed ice were observed to proceed even at 20 K. This indicates that the coexistence of H2O at the surface raises the reactive temperature. In addition, the experiment on H atom exposure was also carried out at 15 K to compare the reaction rate constant between the H and D atoms. The ratio of reaction rate constant k(D)/k(H) obtained is about 0.08 at 15 K. The authors provide information on the potential energy for the H+CO reaction at the surface by using the ratio k(D)/k(H) and by a model calculation of the potential tunneling with the asymmetric Eckart potential. (C) 2007 American Institute of Physics.
  • Akihiro Nagaoka, Naoki Watanabe, Akira Kouchi
    JOURNAL OF PHYSICAL CHEMISTRY A 111 16 3016 - 3028 2007年04月 [査読有り][通常論文]
     
    The surface reactions of CH3OH, CH2DOH, and CHD2OH with cold D atoms at 10 K were investigated using an atomic beam source and FTIR. Methyl-deuterated isotopologues CH2DOH, CHD2OH, and CD3OH were produced by exposure of amorphous solid CH3OH to D atoms at 10 K, and the pseudo-first-order rates for the reactions CH3OH + D -> CH2OH + HD, CH2DOH + D -> CHDOH + HD, and CHD2OH + D -> CD2OH + HD were estimated. The ratios of the reaction rates of the second and third reactions to the first reaction were 0.69 +/- 0.11 and 0.52 +/- 0.14, respectively. The difference in reaction rates is thought to be due to a secondary kinetic isotope effect on the H-abstraction reaction from the methyl side by D atoms.
  • A. Nagaoka, N. Watanabe, A. Kouchi
    J. Phys. Chem. A 111 16 3016 - 3028 2007年03月 [査読有り][通常論文]
  • N. Watanabe, A. Nagaoka, H. Hidaka, T. Shiraki, T. Chigai, A. Kouchi
    PLANETARY AND SPACE SCIENCE 54 11 1107 - 1114 2006年09月 [査読有り][通常論文]
     
    Experiments on the hydrogenation of CO on pure CO and CO-H2O mixed ice have been performed at temperatures between 8 and 20 K. We obtained temperature and compositional dependence of the effective reaction rate constants. Results indicate that hydrogenation proceeds efficiently on pure solid CO and CO-H2O mixed ice at temperatures below 10 and 20 K, respectively. Rate constants for pure CO decreased significantly at 12 K compared to those obtained with CO-H2O mixed ice. Hydrogenation of CO at temperatures greater than 12 K were catalyzed by the H2O adjacent to the CO. The importance of the experimental results for some relevant astrophysical environments has also been outlined. (c) 2006 Elsevier Ltd. All rights reserved.
  • N. Watanabe, A. Nagaoka, H. Hidaka, T. Shiraki, T. Chigai, A. Kouchi
    PLANETARY AND SPACE SCIENCE 54 11 1107 - 1114 2006年09月 [査読有り][通常論文]
     
    Experiments on the hydrogenation of CO on pure CO and CO-H2O mixed ice have been performed at temperatures between 8 and 20 K. We obtained temperature and compositional dependence of the effective reaction rate constants. Results indicate that hydrogenation proceeds efficiently on pure solid CO and CO-H2O mixed ice at temperatures below 10 and 20 K, respectively. Rate constants for pure CO decreased significantly at 12 K compared to those obtained with CO-H2O mixed ice. Hydrogenation of CO at temperatures greater than 12 K were catalyzed by the H2O adjacent to the CO. The importance of the experimental results for some relevant astrophysical environments has also been outlined. (c) 2006 Elsevier Ltd. All rights reserved.
  • A. Nagaoka, N. Watanabe, A. Kouchi
    AIP Conference Proceedings 855 69 - 75 2006年 [査読有り][通常論文]
  • H. Hidaka, N. Watanabe, A. Kouchi
    AIP Conference Proceedings 855 107 - 112 2006年 [査読有り][通常論文]
  • N. Watanabe, H. Hidaka, A. Kouchi
    AIP Conference Proceedings 855 122 - 127 2006年 [査読有り][通常論文]
  • N. Watanabe, H. Hidaka, A. Kouchi
    AIP Conference Proceedings 855 122 - 127 2006年 [査読有り][通常論文]
  • H. Hidaka, N. Watanabe, A. Kouchi
    AIP Conference Proceedings 855 107 - 112 2006年 [査読有り][通常論文]
  • A. Nagaoka, N. Watanabe, A. Kouchi
    AIP Conference Proceedings 855 69 - 75 2006年 [査読有り][通常論文]
  • A. Kouchi, H. Nakano, Y. Kimura, C. Kaito
    Astrophys. J. 626 L129 - L132 2005年05月 [査読有り][通常論文]
  • A. Kouchi, H. Nakano, Y. Kimura, C. Kaito
    Astrophys. J. 626 L129 - L132 2005年05月 [査読有り][通常論文]
  • A. Nagaoka, N. Watanabe, A. Kouchi
    Astrophys. J. 624 L29 - L32 2005年03月 [査読有り][通常論文]
  • A. Nagaoka, N. Watanabe, A. Kouchi
    Astrophys. J. 624 L29 - L32 2005年03月 [査読有り][通常論文]
  • N. Watanabe, A. Nagaoka, T. Shiraki, A. Kouchi
    Astrophys. J. 616 1 638 - 643 2004年11月 [査読有り][通常論文]
  • N. Watanabe, A. Nagaoka, T. Shiraki, A. Kouchi
    Astrophys. J. 616 1 638 - 643 2004年11月 [査読有り][通常論文]
  • H Hidaka, N Watanabe, T Shiraki, A Nagaoka, A Kouchi
    ASTROPHYSICAL JOURNAL 614 2 1124 - 1131 2004年10月 [査読有り][通常論文]
     
    The conversion of formaldehyde (H2CO) to methanol (CH3OH) by successive hydrogenation on H2O ice was measured at 10, 15, and 20 K using atomic hydrogen beams of 30 and 300 K. The conversion rates and CH3OH yields under the 30 K beam are very similar to those under the 300 K beam at all ice temperatures, demonstrating that the reaction is independent of beam temperature. The dependence of the conversion rates on ice temperature is consistent with that for previous experiments on CO hydrogenation. The conversion rate for H2CO --> CH3OH at 15 K was found to be about half that for CO --> H2CO. The dependence of the reactions on the initial thickness of H2CO was also measured. More than 80% of H2CO was converted to CH3OH for H2CO layers of less than 1 monolayer in average thickness. Irradiation of CH3OH with H atoms did not produce H2CO, demonstrating that the reverse process, CH3OH --> H2CO (H abstraction), is minor compared to the forward process.
  • H Hidaka, N Watanabe, T Shiraki, A Nagaoka, A Kouchi
    ASTROPHYSICAL JOURNAL 614 2 1124 - 1131 2004年10月 [査読有り][通常論文]
     
    The conversion of formaldehyde (H2CO) to methanol (CH3OH) by successive hydrogenation on H2O ice was measured at 10, 15, and 20 K using atomic hydrogen beams of 30 and 300 K. The conversion rates and CH3OH yields under the 30 K beam are very similar to those under the 300 K beam at all ice temperatures, demonstrating that the reaction is independent of beam temperature. The dependence of the conversion rates on ice temperature is consistent with that for previous experiments on CO hydrogenation. The conversion rate for H2CO --> CH3OH at 15 K was found to be about half that for CO --> H2CO. The dependence of the reactions on the initial thickness of H2CO was also measured. More than 80% of H2CO was converted to CH3OH for H2CO layers of less than 1 monolayer in average thickness. Irradiation of CH3OH with H atoms did not produce H2CO, demonstrating that the reverse process, CH3OH --> H2CO (H abstraction), is minor compared to the forward process.
  • H. Nakano, A. Kouchi, S. Tachibana, A. Tsuchiyama
    Astrophys. J. 592 2 1252 - 1262 2003年08月 [査読有り][通常論文]
  • H Nakano, A Kouchi, S Tachibana, A Tsuchiyama
    ASTROPHYSICAL JOURNAL 592 2 1252 - 1262 2003年08月 [査読有り][通常論文]
     
    A series of evaporation experiments was performed on interstellar organic analogs under high vacuum in order to study the distribution of interstellar organic materials in the solar nebula. Temperature dependences of the weight loss of the samples and the elemental composition of the evaporation residue were examined. The chemical composition of evaporated gases during heating was also investigated. It was found on the basis of the experimental results and the astrophysical model for the solar nebula that there would be molecular cloud and diffuse cloud organic materials at heliocentric distances larger than 2.7 and 2.1 AU, respectively, in the late evolution stage of the disk. Very reductive gas was evaporated at around 2.4 AU during the evaporation of diffuse cloud organic materials, and this causes very reduced condition in the solar nebula. We discuss a redox state of chondrites based on our experimental result and conclude that ordinary chondrites would form at heliocentric distances of less than 2.2 AU, enstatite chondrites at around 2.4 AU, and carbonaceous chondrites at heliocentric distances larger than 3.0 AU. From the comparison of carbon and nitrogen contents in evaporation residues of interstellar organic analogs with those in carbonaceous chondrites, it is concluded that the C and N contents in carbonaceous chondrites cannot be explained by the heating of interstellar organic dusts before accretion to parent bodies.
  • N. Watanabe, T. Shiraki, A.Kouchi
    Astrophys. J. 588 2 L121 - L124 2003年04月 [査読有り][通常論文]
  • N. Watanabe, T. Shiraki, A.Kouchi
    Astrophys. J. 588 2 L121 - L124 2003年04月 [査読有り][通常論文]
  • Impact process of ice in the solar system
    M. Arakawa, A. Kouchi
    High-Pressure Shock Compression of Solids V: Shock Chemistry With Applications to Meteorite Impacts 199 - 231 2003年 [査読無し][通常論文]
  • Impact process of ice in the solar system
    M. Arakawa, A. Kouchi
    High-Pressure Shock Compression of Solids V: Shock Chemistry With Applications to Meteorite Impacts 199 - 231 2003年 [査読無し][通常論文]
  • T. Kudo, A. Kouchi, M.Arakawa, H. Nakano
    Meteoritics Planet. Sci. 37 12 1975 - 1983 2002年12月 [査読有り][通常論文]
  • H. Nakano, A. Kouchi, M. Arakawa, Y. Kimura, C. Kaito, H. Ohno, T. Hondoh
    Proc. Jpn. Acad.SerB 78B 9 277 - 281 2002年12月 [査読有り][通常論文]
  • H. Nakano, A. Kouchi, M. Arakawa, Y. Kimura, C. Kaito, H. Ohno, T. Hondoh
    Proc. Jpn. Acad.SerB 78B 9 277 - 281 2002年12月 [査読有り][通常論文]
  • T. Kudo, A. Kouchi, M.Arakawa, H. Nakano
    Meteoritics Planet. Sci. 37 12 1975 - 1983 2002年12月 [査読有り][通常論文]
  • N. Watanabe, A. Kouchi
    Astrophys. J. Lett. 571 2 L173 - L176 2002年05月 [査読有り][通常論文]
  • N. Watanabe, A. Kouchi
    Astrophys. J. Lett. 571 2 L173 - L176 2002年05月 [査読有り][通常論文]
  • N. Watanabe, A. Kouchi
    Astrophys. J. 567 1 651 - 655 2002年03月 [査読有り][通常論文]
  • N. Watanabe, A. Kouchi
    Astrophys. J. 567 1 651 - 655 2002年03月 [査読有り][通常論文]
  • H. Hashimoto, K. Ushio, T. Kaneko, K.Kobayashi, J. M.Greenberg, M.Yamashita, A. Brack, L. Colangeli, G. Horneck, Y. Ishikawa, A. Kouchi, R.Navarro-Gonzalez, T. Oshima, F. Raulin, T. Saito
    Adv. Space Res. 30 6 1495 - 1500 2002年 [査読有り][通常論文]
  • A. Kouchi, T. Kudo, H. Nakano, M. Arakawa, N.Watanabe, S. Sirono, M. Higa, N. Maeno
    Astrophys. J. 566 2 L121 - L124 2002年01月 [査読有り][通常論文]
  • H. Hashimoto, K. Ushio, T. Kaneko, K.Kobayashi, J. M.Greenberg, M.Yamashita, A. Brack, L. Colangeli, G. Horneck, Y. Ishikawa, A. Kouchi, R.Navarro-Gonzalez, T. Oshima, F. Raulin, T. Saito
    Adv. Space Res. 30 6 1495 - 1500 2002年 [査読有り][通常論文]
  • A. Kouchi, T. Kudo, H. Nakano, M. Arakawa, N.Watanabe, S. Sirono, M. Higa, N. Maeno
    Astrophys. J. 566 2 L121 - L124 2002年01月 [査読有り][通常論文]
  • A Kouchi, S Sirono
    GEOPHYSICAL RESEARCH LETTERS 28 5 827 - 830 2001年03月 [査読有り][通常論文]
     
    We report new results of Differential Thermal Analysis (DTA) of crystallization of impure amorphous H(2)O ice (a-H(2)O), containing CO, CO(2) and CH(4) molecules. It is revealed that the heat of crystallization of impure a-H(2)O is reduced by the impurities. The crystallization is not exothermic like pure; a-H(2)O, but endothermic when the concentration of impurities is higher than 2% regardless of molecular species. An out-gassing rate from a model cometary nucleus is computed numerically using the experimental values. The result shows that the runaway crystallization of cometary ice never occurs and that the mechanism of outbursts should be reexamined.
  • A Kouchi, S Sirono
    GEOPHYSICAL RESEARCH LETTERS 28 5 827 - 830 2001年03月 [査読有り][通常論文]
     
    We report new results of Differential Thermal Analysis (DTA) of crystallization of impure amorphous H(2)O ice (a-H(2)O), containing CO, CO(2) and CH(4) molecules. It is revealed that the heat of crystallization of impure a-H(2)O is reduced by the impurities. The crystallization is not exothermic like pure; a-H(2)O, but endothermic when the concentration of impurities is higher than 2% regardless of molecular species. An out-gassing rate from a model cometary nucleus is computed numerically using the experimental values. The result shows that the runaway crystallization of cometary ice never occurs and that the mechanism of outbursts should be reexamined.
  • N Watanabe, T Horii, A Kouchi
    ASTROPHYSICAL JOURNAL 541 2 772 - 778 2000年10月 [査読有り][通常論文]
     
    We have carried out experiments on the formation of D-2 molecules from amorphous D2O ice (thickness: 40, 120 Angstrom) by UV irradiation (lambda: 126, 172 Ka) at 12 K. Our results show that most of the D-2 products remain in and on the amorphous ice at 12 K; directly photodesorbed D-2 was little observed at 12 K. The amount of D2O destruction and D-2 yields after a dose of 10(18) photons cm(-2) at 12 K were about 10%-20% and 1%-2% of the initial number of D2O molecules, respectively. The formation reaction of D-2 was found to be a single-photon process via the first excited state of D2O. The reconstruction of D2O at 12 K (reverse reaction) was not observed within our experimental timescale (5 hr). We estimated the cross sections for the D2O destruction and the D-2 formation reactions by the photon impact at 12 K for the first time.
  • N Watanabe, T Horii, A Kouchi
    ASTROPHYSICAL JOURNAL 541 2 772 - 778 2000年10月 [査読有り][通常論文]
     
    We have carried out experiments on the formation of D-2 molecules from amorphous D2O ice (thickness: 40, 120 Angstrom) by UV irradiation (lambda: 126, 172 Ka) at 12 K. Our results show that most of the D-2 products remain in and on the amorphous ice at 12 K; directly photodesorbed D-2 was little observed at 12 K. The amount of D2O destruction and D-2 yields after a dose of 10(18) photons cm(-2) at 12 K were about 10%-20% and 1%-2% of the initial number of D2O molecules, respectively. The formation reaction of D-2 was found to be a single-photon process via the first excited state of D2O. The reconstruction of D2O at 12 K (reverse reaction) was not observed within our experimental timescale (5 hr). We estimated the cross sections for the D2O destruction and the D-2 formation reactions by the photon impact at 12 K for the first time.
  • Design of the cosmobiology experiments in earth orbit to test abiotic formation of bioorganic compounds
    H. Hashimoto, K. Ushio, T. Kaneko, K. Kobayashi, A. Brack, L. Colangeli, J. M. Greenberg, G.. Horneck, A. Kouchi, R. Navarro-Gonzalez, A. Grack, F. Raulin, T. Saito, M. Yamashita
    Origin Life Evol. Bioshpere 30 154  2000年08月 [査読有り][通常論文]
  • Design of the cosmobiology experiments in earth orbit to test abiotic formation of bioorganic compounds
    H. Hashimoto, K. Ushio, T. Kaneko, K. Kobayashi, A. Brack, L. Colangeli, J. M. Greenberg, G.. Horneck, A. Kouchi, R. Navarro-Gonzalez, A. Grack, F. Raulin, T. Saito, M. Yamashita
    Origin Life Evol. Bioshpere 30 154  2000年08月 [査読有り][通常論文]
  • K. Kobayashi, T. Kaneko, A. Kouchi, H. Hashimoto, T. Saito, M. Yamashita
    Adv. Space Res. 23 2 401 - 404 1999年 [査読有り][通常論文]
  • K. Kobayashi, T. Kaneko, A. Kouchi, H. Hashimoto, T. Saito, M. Yamashita
    Adv. Space Res. 23 2 401 - 404 1999年 [査読有り][通常論文]
  • H. Hashimoto, J.M. Greenberg, A. Grack, L. Colangeli, G. Horneck, R. Navarro-Gonzalez, F. Raulin, A. Kouchi, T. Saito, M. Yamashita, K. Kobayashi
    JPN. Soc. Biol. Sci. Space 12 2 106 - 111 1998年12月 [査読無し][通常論文]
  • H. Hashimoto, J.M. Greenberg, A. Brack, L. Colangeli, G. Horneck, R. Navarro-Gonzalez, F. Raulin, A. Kouchi, T. Saito, M. Yamashita, K. Kobayashi
    JPN. Soc. Biol. Sci. Space 12 2 106 - 111 1998年12月 [査読無し][通常論文]
  • N. Sugi, M. Arakawa, A. Kouchi, N. Maeno
    Geophys. Res. Lett. 25 6 837 - 840 1998年03月 [査読有り][通常論文]
  • N. Sugi, M. Arakawa, A. Kouchi, N. Maeno
    Geophys. Res. Lett. 25 6 837 - 840 1998年03月 [査読有り][通常論文]
  • Amorphous water ice-a solar system material
    P. Jenniskens, D. F. Blake, A. Kouchi
    Solar System Ices 227 139 - 155 1998年 [査読有り][通常論文]
  • 古川義純, 香内 晃, 山本正樹, 黒田登志雄
    日本結晶学会誌 30 5 279 - 285 1998年 [査読有り][通常論文]
  • Amorphous water ice-a solar system material
    P. Jenniskens, D. F. Blake, A. Kouchi
    Solar System Ices 227 139 - 155 1998年 [査読有り][通常論文]
  • COSMOGLACIOLOGY - EVOLUTION OF ICE IN INTERSTELLAR SPACE AND THE EARLY SOLAR-SYSTEM
    A KOUCHI, T YAMAMOTO
    PROGRESS IN CRYSTAL GROWTH AND CHARACTERIZATION OF MATERIALS 30 2-3 83 - 108 1995年 [査読有り][通常論文]
     
    This paper reviews the present status of the study of interstellar icy grains and formation of the solar system from a point of view of condensation and sublimation of ices. The ices discussed here includes not only crystalline H2O ice but also amorphous H2O ice and multicomponent ices which are formed by condensation of H2O, CO, CO2, CH4, and other volatile molecular species. Emphasis is place on showing how the various thermal properties of ices are related to the study the evolution of interstellar matter and the origin of the solar system. We concentrate on the topics of (1) the observed and theoretically inferred composition and structure of ices in space, (2) their crystalline structure, and (3) the sublimation behavior of amorphous ice and multicomponent ices. In (2) the conditions for formation and preservation of amorphous ice are given which may be applicable to astrophysical ices as well as amorphous solids in general. Discussion is given on the crystallinity of ices in various astrophysical environment and its relevance to the origin of the solar system. In (3) we discuss the present problems in establishing a ''cosmic thermometer'' with the use of the sublimation behaviors of ices for the study of the thermal histories of interstellar ices and solar system icy bodies.
  • COSMOGLACIOLOGY - EVOLUTION OF ICE IN INTERSTELLAR SPACE AND THE EARLY SOLAR-SYSTEM
    A KOUCHI, T YAMAMOTO
    PROGRESS IN CRYSTAL GROWTH AND CHARACTERIZATION OF MATERIALS 30 2-3 83 - 108 1995年 [査読有り][通常論文]
     
    This paper reviews the present status of the study of interstellar icy grains and formation of the solar system from a point of view of condensation and sublimation of ices. The ices discussed here includes not only crystalline H2O ice but also amorphous H2O ice and multicomponent ices which are formed by condensation of H2O, CO, CO2, CH4, and other volatile molecular species. Emphasis is place on showing how the various thermal properties of ices are related to the study the evolution of interstellar matter and the origin of the solar system. We concentrate on the topics of (1) the observed and theoretically inferred composition and structure of ices in space, (2) their crystalline structure, and (3) the sublimation behavior of amorphous ice and multicomponent ices. In (2) the conditions for formation and preservation of amorphous ice are given which may be applicable to astrophysical ices as well as amorphous solids in general. Discussion is given on the crystallinity of ices in various astrophysical environment and its relevance to the origin of the solar system. In (3) we discuss the present problems in establishing a ''cosmic thermometer'' with the use of the sublimation behaviors of ices for the study of the thermal histories of interstellar ices and solar system icy bodies.
  • A. Kouchi, T. Yamamoto, T. Kozasa, T. Kuroda, J. M. Greenberg
    Astron. Astrophys. 290 1009 - 1018 1994年02月 [査読有り][通常論文]
  • A. Kouchi, T. Yamamoto, T. Kozasa, T. Kuroda, J. M. Greenberg
    Astron. Astrophys. 290 1009 - 1018 1994年02月 [査読有り][通常論文]
  • JM GREENBERG, A KOUCHI, W NIESSEN, H IRTH, J VANPARADIJS, M DEGROOT, W HERMSEN
    JOURNAL OF BIOLOGICAL PHYSICS 20 1-4 61 - 70 1994年 [査読有り][通常論文]
     
    The physical, chemical and astrophysical processes by which chiral prebiotic molecules can be produced in interstellar dust and later delivered ''safely'' to the earth are considered. A laboratory analog experiment on the irradiation by circularly polarized UV light of mirror image molecules at the low temperatures of interstellar dust demonstrates that a substantial degree of chirality can be produced by irradiation of the dust by circularly polarized light from pulsars whose mean brightness and distribution in the Milky Way provide the energetic photons. The chirality is then preserved by cold aggregation of the dust into low density fragile nuclei. The thermal evolution of comets following them from birth through billions of years in the Oort cloud and back to the inner solar system results in preservation of dust organics in largely pristine form - even including effects of radiogenic heating. Physical justification for the cushioned transfer of fragments of the fluffy comets impacting the earth's atmosphere provides a conceptual basis for depositing significant concentrations of interstellar prebiotic molecules. Chiral amplification in water on the earth is presumed to be enhanced by this local concentration. If chiral molecules are discovered in comet nucleus material which will some day be returned to the laboratory, we may have in our hands the same building blocks from which we evolved.
  • JM GREENBERG, A KOUCHI, W NIESSEN, H IRTH, J VANPARADIJS, M DEGROOT, W HERMSEN
    JOURNAL OF BIOLOGICAL PHYSICS 20 1-4 61 - 70 1994年 [査読有り][通常論文]
     
    The physical, chemical and astrophysical processes by which chiral prebiotic molecules can be produced in interstellar dust and later delivered ''safely'' to the earth are considered. A laboratory analog experiment on the irradiation by circularly polarized UV light of mirror image molecules at the low temperatures of interstellar dust demonstrates that a substantial degree of chirality can be produced by irradiation of the dust by circularly polarized light from pulsars whose mean brightness and distribution in the Milky Way provide the energetic photons. The chirality is then preserved by cold aggregation of the dust into low density fragile nuclei. The thermal evolution of comets following them from birth through billions of years in the Oort cloud and back to the inner solar system results in preservation of dust organics in largely pristine form - even including effects of radiogenic heating. Physical justification for the cushioned transfer of fragments of the fluffy comets impacting the earth's atmosphere provides a conceptual basis for depositing significant concentrations of interstellar prebiotic molecules. Chiral amplification in water on the earth is presumed to be enhanced by this local concentration. If chiral molecules are discovered in comet nucleus material which will some day be returned to the laboratory, we may have in our hands the same building blocks from which we evolved.
  • P. Jenniskens, G. A. Baratta, A. Kouchi, M. S. de Groot, J. M. Greenberg, G. Strazzulla
    Astron. Astrophys. 273 583 - 600 1993年12月 [査読有り][通常論文]
  • P. Jenniskens, G. A. Baratta, A. Kouchi, M. S. de Groot, J. M. Greenberg, G. Strazzulla
    Astron. Astrophys. 273 583 - 600 1993年12月 [査読有り][通常論文]
  • 化学と生物 31,708-713 1993年 [査読無し][通常論文]
  • アモルファス氷の熱伝導率と慧星の熱史
    天文月報 87,15-20 1993年 [査読無し][通常論文]
  • A new measurement of thermal conductivity of amorphous ice: preservation of protosolar nebula matter in comets
    A. Kouchi, J. M.Greenberg, T. Yamamoto, T. Mukai, Z. F. Xing
    Physics and Chemistry of Ice 229 - 236 1992年04月 [査読有り][通常論文]
  • A. Kouchi, J. M. Greenberg, T. Yamamoto, T. Mukai
    Astrophys. J. 388 4 L73 - L76 1992年04月 [査読無し][通常論文]
  • A. Kouchi, J. M. Greenberg, T. Yamamoto, T. Mukai
    Astrophys. J. 388 4 L73 - L76 1992年04月 [査読無し][通常論文]
  • A new measurement of thermal conductivity of amorphous ice: preservation of protosolar nebula matter in comets
    A. Kouchi, J. M.Greenberg, T. Yamamoto, T. Mukai, Z. F. Xing
    Physics and Chemistry of Ice 229 - 236 1992年04月 [査読有り][通常論文]
  • A. Kouchi, T. Kuroda
    Jpn. J. Appl. Phys 29 5 L807 - L809 1990年05月 [査読有り][通常論文]
  • A. Kouchi, T. Kuroda
    Jpn. J. Appl. Phys 29 5 L807 - L809 1990年05月 [査読有り][通常論文]
  • A KOUCHI, T KURODA
    NATURE 344 6262 134 - 135 1990年03月 [査読有り][通常論文]
  • A KOUCHI, T KURODA
    NATURE 344 6262 134 - 135 1990年03月 [査読有り][通常論文]
  • Evaporation of H2O-CO2-CH4-CO ice and its implication for the evolution of ice grains
    A. Kouchi, T. Kuroda
    "Proc. 24th ESLAB Symp. on the Formation of Stars and Planets, and the Evolution of the Solar System 193 - 196 1990年 [査読有り][通常論文]
  • A. Kouchi
    J. Cryst. Growth 99 1220 - 1226 1990年01月 [査読有り][通常論文]
  • A KOUCHI
    JOURNAL OF CRYSTAL GROWTH 99 1-4 1220 - 1226 1990年01月 [査読有り][通常論文]
  • A KOUCHI
    NATURE 330 6148 550 - 552 1987年12月 [査読有り][通常論文]
  • A. Kouchi, Y. Furukawa, T. Kuroda
    J. Phys. Colloques 48 C1-3 675 - 677 1987年12月 [査読有り][通常論文]
  • A KOUCHI, Y FURUKAWA, T KURODA
    JOURNAL DE PHYSIQUE 48 C-1 675 - 677 1987年03月 [査読有り][通常論文]
  • A. Kouchi
    Nature 330 6148 550 - 552 1987年 [査読有り][通常論文]
  • KOUCHI A, TSUCHIYAMA A, SUNAGAWA I
    Contrib. Mineral. Petrol. 93 4 429 - 438 1986年08月 [査読無し][通常論文]
  • Contributions to Mineralogy and Petrology 93 1986年 [査読無し][通常論文]
  • A KOUCHI, Y SUGAWARA, K KASHIMA, SUNAGAWA, I
    CONTRIBUTIONS TO MINERALOGY AND PETROLOGY 83 1-2 177 - 184 1983年 [査読有り][通常論文]
  • A KOUCHI, S HOSOYA, M KITAMURA, H TAKEI, SUNAGAWA, I
    PHYSICS AND CHEMISTRY OF MINERALS 9 3-4 167 - 172 1983年 [査読有り][通常論文]
  • A KOUCHI, SUNAGAWA, I
    NATURE 304 5926 527 - 528 1983年 [査読有り][通常論文]
  • A KOUCHI, Y SUGAWARA, K KASHIMA, SUNAGAWA, I
    CONTRIBUTIONS TO MINERALOGY AND PETROLOGY 83 1-2 177 - 184 1983年 [査読有り][通常論文]
  • A KOUCHI, S HOSOYA, M KITAMURA, H TAKEI, SUNAGAWA, I
    PHYSICS AND CHEMISTRY OF MINERALS 9 3-4 167 - 172 1983年 [査読有り][通常論文]
  • A KOUCHI, SUNAGAWA, I
    NATURE 304 5926 527 - 528 1983年 [査読有り][通常論文]
  • Experimental study of mixing of basaltic and dacitic magmas
    A. Kouchi, I. Sunagawa
    Sci. Rep. Tohoku Univ. Ser. III 15 163 - 175 1982年 [査読有り][通常論文]
  • M. Kitamura, A. Kouchi, S. Hosoya, I. Sunagawa
    Mineral. J. 11 3 119 - 137 1982年 [査読有り][通常論文]
  • M. Kitamura, A. Kouchi, S. Hosoya, I. Sunagawa
    Mineral. J. 11 3 119 - 137 1982年 [査読有り][通常論文]
  • Experimental study of mixing of basaltic and dacitic magmas
    A. Kouchi, I. Sunagawa
    Sci. Rep. Tohoku Univ. Ser. III 15 163 - 175 1982年 [査読有り][通常論文]

講演・口頭発表等

  • Development of an ultrahigh vacuum transmission electron mircoscope for in-situ observation of ice  [通常講演]
    A.Kouchi, N.Waranabe, H. Hidaka, T.Hama, S. Nakatubo, K. Fujita, K. Sinbori, M. Ikeda
    3th International Conference on the Physics and Chemistry of Ice(PCI-2014) 2014年03月 Hanover, US
  • 宇宙における分子進化:星間雲から原始惑星系へ  [招待講演]
    香内 晃
    2013年度日本地球化学会第60回年会 2013年09月 口頭発表(招待・特別) 筑波大学
  • Development of an ultrahigh vacuum low temperature transmission electron microscope for in situ observation of ice  [通常講演]
    A. Kouchi, N. Watanabe, H. Hidaka, T. Hama, S. Nakatsubo, K. Fujita, K. Sinbori, M.Ikeda
    First Workshop on Experimental Laboratory Astrophysics 2013年02月 ポスター発表 Kauai, Hawaii
  • Towards a new era in physics and chemistry of ice at ILTS  [通常講演]
    A. Kouchi
    12th International Conference on the Physics and Chemistry of Ice 2010年 口頭発表(招待・特別) Sapporo,Japan
  • Formation of interstellar ice by low temperature surface atomic reactions  [招待講演]
    A. Kouchi, Y. Oba, N. Miyauchi, H. Hidaka, N. Watanabe
    CRYO2009 2009年 口頭発表(招待・特別) Sapporo,Japan
  • 極低温表面原子反応による分子雲での分子進化  [招待講演]
    香内 晃
    JPGU Meeting 2009 2009年 口頭発表(招待・特別) Chiba, Japan
  • Diamond Formation in Interstellar Clouds and Parent Bodies of Carbonaceous Chondrites  [招待講演]
    A. Kouchi
    19th General Meeting of the International Mineralogical Association 2006年 口頭発表(招待・特別) Kobe, Japan
  • Formation of organic molecules by the tunneling reaction of H with solid CO on interstellar grain”, Misasa International Symposium  [招待講演]
    A.Kouchi, N.Watanabe
    2006年 口頭発表(招待・特別) Kurayoshi, Japan
  • Origin of cometary H2CO and CH3OH  [招待講演]
    A.Kouchi, A.Nagaoka, H.Shiraki, H.Hidaka, N.Watanabe
    Asia-Oceania Geosciences Society Annual Meeting 2004年 口頭発表(招待・特別) Singapore
  • From interstellar organic grains to asteroids  [招待講演]
    A.Kouchi
    Physical properties of NEOs 2001年 口頭発表(招待・特別) Erice, Italy
  • New methods for making amorphous icy grains  [招待講演]
    A. Kouchi
    ISSI Workshop on "The role of laboratory experiments in the characterization of cosmic materials" 2000年 口頭発表(招待・特別) Bern
  • Conditions for Condensation and Preservation of Amorphous Ice and Crystallinity of Astrophysical Ices  [招待講演]
    A.Kouchi
    International School of Space Chemistry 1994年 口頭発表(招待・特別) Erice,Italy
  • Physical Properties of Impurity-doped Amorphous Ice, Relevance to Comet Evolution  [招待講演]
    A.Kouchi
    International School of Space Chemistry 1994年 口頭発表(招待・特別) Erice,Italy
  • Condensation of amorphous and crystalline ices in space  [招待講演]
    A.Kouchi, T.Kuroda
    29th International Geological Congress 1992年 口頭発表(招待・特別) Kyoto, Japan

受賞

  • 1986年 井上研究奨励金

共同研究・競争的資金等の研究課題

  • アモルファス氷の物性
  • 彗星の起源と進化
  • Physical Properties of Amorphous Ice
  • Origin and Evolution of Comets

教育活動情報

主要な担当授業

  • 宇宙低温物質科学特論
    開講年度 : 2018年
    課程区分 : 修士課程
    開講学部 : 理学院
    キーワード : アモルファス氷,結晶氷,星間塵,彗星,氷天体

大学運営

学内役職歴

  • 2013年4月1日 - 2015年3月31日 企画・経営室室員
  • 2015年4月1日 - 2017年3月31日 企画・経営室室員
  • 2017年4月1日 - 2019年3月31日 研究戦略室室員
  • 2017年4月1日 - 2019年3月31日 総長補佐
  • 2019年4月1日 -  研究戦略室室員
  • 2019年4月1日 -  総長補佐


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