Researcher Database

Hiroshi Hidaka
Institute of Low Temperature Science Frontier Ice and Snow Science
Assistant Professor

Researcher Profile and Settings

Affiliation

  • Institute of Low Temperature Science Frontier Ice and Snow Science

Job Title

  • Assistant Professor

J-Global ID

Research Interests

  • 星間塵   低温表面反応   REMPI   水素分子   反応熱   星間化学   惑星間空間   重水素濃集   低温   原子反応   地球外物質化学   氷表面反応   表面   アモルファス氷   トンネル反応   極低温表面反応   同位体分別   星間分子   

Research Areas

  • Natural sciences / Space and planetary science
  • Natural sciences / Space and planetary science
  • Natural sciences / Solid earth science

Academic & Professional Experience

  • 2012 Hokkaido University Institute of Low Temperature Science

Education

  •        - 2003  Tokyo Metropolitan University  Graduate School of Science  Department of Physics
  •        - 2003  Tokyo Metropolitan University  Graduate School, Division of Natural Science
  •        - 2000  Tokyo Metropolitan University  Graduate School of Science
  •        - 2000  Tokyo Metropolitan University  Graduate School, Division of Natural Science
  •        - 1998  Hosei University
  •        - 1998  Hosei University  Faculty of Engineering

Association Memberships

  • 日本惑星科学会   原子衝突研究協会   日本物理学会   The Japanese Society for Planetary Sciences   The Societry for Atomic Collision Research   The Physical Society of Japan   

Research Activities

Published Papers

  • Ultraviolet-photon exposure stimulates negative current conductivity in amorphous ice below 50 K
    N. Watanabe, W. M. C. Sameera, H. Hidaka, A. Miyazaki, A. Kouchi
    Chemical Physics Letters 737 136820  2019 [Refereed][Not invited]
  • 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
    日本雪氷学会誌 雪氷 in press 2018 [Refereed][Not invited]
  • 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  2017/09 [Refereed][Not invited]
     
    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.
  • Rafael Escribano, Emilio Artacho, Akira Kouchi, Tetusya Hama, Yuki Kimura, Hiroshi Hidaka, Naoki Watanabe
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS 19 (10) 7280 - 7287 1463-9076 2017/03 [Refereed][Not invited]
     
    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.
  • Hitomi Kobayashi, Hiroshi Hidaka, Thanja Lamberts, Tetsuya Hama, Hideyo Kawakita, Johannes Kaestner, Naoki Watanabe
    ASTROPHYSICAL JOURNAL 837 (2) 155 - 169 0004-637X 2017/03 [Refereed][Not invited]
     
    We quantitatively investigated the hydrogen addition reactions of acetylene (C2H2) and ethylene (C2H4) on amorphous solid water (ASW) at 10 and 20 K relevant to the formation of ethane (C2H6) on interstellar icy grains. We found that the ASW surface enhances the reaction rates for C2H2 and C2H4 by approximately a factor of 2 compared to those on the pure- solid C2H2 and C2H4 at 10 K, probably due to an increase in the sticking coefficient and adsorption energy of the H atoms on ASW. In contrast to the previous proposal that the hydrogenation rate of C2H4 is orders of magnitude larger than that of C2H2, the present results show that the difference in hydrogenation rates of C2H2 and C2H4 is only within a factor of 3 on both the surfaces of pure solids and ASW. In addition, we found the small kinetic isotope effect for hydrogenation/deuteration of C2H2 and C2H4 at 10 K, despite the requirement of quantum tunneling. At 20 K, the reaction rate of deuteration becomes even larger than that of hydrogenation. These unusual isotope effects might originate from a slightly larger number density of D atoms than H atoms on ASW at 20 K. The hydrogenation of C2H2 is four times faster than CO hydrogenation and can produce C2H6 efficiently through C2H4 even in the environment of a dark molecular cloud.
  • A. Kouchi, T. Hama, Y. Kimura, H. Hidaka, R. Escribano, N. Watanabe
    CHEMICAL PHYSICS LETTERS 658 287 - 292 0009-2614 2016/08 [Refereed][Not invited]
     
    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.
  • Yoichi Nakai, Hiroshi Hidaka, Naoki Watanabe, Takao M. Kojima
    JOURNAL OF CHEMICAL PHYSICS 144 (22) 224306  0021-9606 2016/06 [Refereed][Not invited]
     
    We measured equilibrium constants for H3O+(H2O)(n-1) + H2O <-> H3O+(H2O)(n) (n = 4-9) reactions taking place in an ion drift tube with various applied electric fields at gas temperatures of 238-330 K. The zero-field reaction equilibrium constants were determined by extrapolation of those obtained at non-zero electric fields. From the zero-field reaction equilibrium constants, the standard enthalpy and entropy changes, Delta H-n,n-1(0) and Delta S-n, n-1(0), of stepwise association for n = 4-8 were derived and were in reasonable agreement with those measured in previous studies. We also examined the electric field dependence of the reaction equilibrium constants at non-zero electric fields for n = 4-8. An effective temperature for the reaction equilibrium constants at non-zero electric field was empirically obtained using a parameter describing the electric field dependence of the reaction equilibrium constants. Furthermore, the size dependence of the parameter was thought to reflect the evolution of the hydrogen-bond structure of H3O+(H2O)(n) with the cluster size. The reflection of structural information in the electric field dependence of the reaction equilibria is particularly noteworthy. Published by AIP Publishing.
  • H. Hidaka, M. Watanabe, A. Kouchi, N. Watanabe
    FIRST INTERNATIONAL CONFERENCE ON CHEMICAL EVOLUTION OF STAR FORMING REGION AND ORIGIN OF LIFE (ASTROCHEM2012) 1543 318 - 325 0094-243X 2013 [Refereed][Not invited]
     
    The elucidation of formation pathways and mechanisms of deuterated species that have been detected by astronomical observations is important in studying chemical evolution in space. Formaldehyde and methanol are well-known molecules not only as reaction products on grain surfaces, but also as highly deuterated molecules. We have conducted experimental studies to clarify the formation mechanisms of deuterated formaldehyde and methanol on low temperature solid surfaces. In this paper, we summarize our experimental findings of the exposure of solid H2CO and D2CO on amorphous solid water to D and H atoms at 10-20 K, respectively. The isotope exchange reactions were observed in both reaction systems of D + H2CO and H + D2CO. In contrast, the addition reactions were only observed in the H + D2CO system because D addition to H2CO is much slower than isotope exchange. This isotope dependence on the reaction pathways can be explained by the quantum tunneling effect.
  • Y. Oba, N. Watanabe, T. Hama, K. Kuwahata, H. Hidaka, A. Kouchi
    Astrophysical Journal 749 (1) 67 - 78 1538-4357 2012/04/10 [Refereed][Not invited]
     
    The present study experimentally demonstrated that solid H2O is formed through the surface reaction OH+ H2 at 10K. This is the first experimental evidence of solid H2O formation using hydrogen in its molecular form at temperatures as low as 10K. We further found that H 2O formation through the reaction OH+ H2 is about one order of magnitude more effective than HDO formation through the reaction OH+ D2. This significant isotope effect results from differences in the effective mass of each reaction, indicating that the reactions proceed through quantum tunneling. © 2012. The American Astronomical Society. All rights reserved.
  • 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 0388-5321 2012 [Not refereed][Not invited]
  • H. Hidaka, M. Watanabe, A. Kouchi, N, Watanabe
    Physical Chemistry Chemical Physics 13 (35) 15798 - 15802 1463-9076 2011 [Refereed][Not invited]
  • Formation of H2O Ice through the Surface Reaction O2 + H at Low Temperatures: Reaction Kinetics and Structure of the Ice
    Oba, Y, Miyauchi, N, Chigai, T, Hidaka, H, Watanabe, N, Kouchi, A
    Physics and Chemistry of Ice 2010, eds. Y. Furukawa, G. Sazaki, T. Uchida, N. Watanabe, Hokkaido University Press, Sapporo, ISBN: 978-4-8329-0361-6 361 - 368 2011 [Not refereed][Not invited]
  • Sequential hydrogenation of molecular oxygen on cold surfaces: reaction kinetics and structure of formed H2O ice
    Y.Oba, N.Miyauchi, H.Hidaka, T.Chigai, N.Watanabe, A.Kouchi
    Proceedings of the International Astronomical Union 280 2011 [Refereed][Not invited]
  • A. Kouchi, N. Watanabe, H. Hidaka, N. Miyauchi, Y. Oba, T. Chigai
    Astron. Soc. Pacific Conf. Ser. 414 338 - 346 2010 [Refereed][Not invited]
  • Watanabe Naoki, Kouchi Akira, Hidaka Hiroshi, Kimura Yuki, Hama Tetsuya
    Abstracts of Papers of the American Chemical Society 239 2010 [Refereed][Not invited]
  • H. Hidaka, M. Watanabe, A. Kouchi, N. Watanabe
    ASTROPHYSICAL JOURNAL 702 (1) 291 - 300 0004-637X 2009/09 [Refereed][Not invited]
     
    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.
  • Y. Oba, N. Miyauchi, H. Hidaka, T. Chigai, N. Watanabe, A. Kouchi
    ASTROPHYSICAL JOURNAL 701 (1) 464 - 470 0004-637X 2009/08 [Refereed][Not invited]
     
    Formation of H2O molecules through the codeposition of oxygen molecules and hydrogen atoms is examined in situ using IR spectroscopy at 10-40 K under various O-2 and H fluxes. It is found that H2O and H2O2 are continuously formed by reaction, even at 40 K. The H2O ice formed is amorphous, but has a compact (not microporous) structure compared to vapor-deposited amorphous H2O ice, because dangling OH bonds are not observed in the IR spectrum. This is consistent with astronomical observations in molecular clouds and theoretical predictions, which suggest that hydrogenation of O-2 is one of the potential routes for reproducing these IR spectral characteristics. The composition of the ice formed by codeposition varies with the O-2/H ratio and temperature. Although no data are available at present for the H2O/H2O2 ratio of ice in molecular clouds, this study suggests that hydrogenation of O-2 has a potential to yield a H2O/H2O2 ratio of 5 or more in molecular clouds.
  • Hydrogen isotope exchange and H(D) atom addition reaction of solid formaldehyde on amorphous solid water at low temperatures
    H. Hidaka, M. Watanabe, A. Kouchi, N. Watanabe
    Journal of physics: Conference series 194 132024  2009 [Refereed][Not invited]
  • 大場康弘, 宮内直弥, 千貝健, 日高宏, 渡部直樹, 香内 晃
    地球化学 43 117 - 131 2009 [Refereed][Not invited]
  • N. Watanabe, A. Kouchi, H. Hidaka, Y. Oba, N. Miyauchi
    Journal of Physics: Conference Series 194 (1) 012044  1742-6596 2009 [Refereed][Not invited]
     
    Reactions of atomic hydrogen with CO and O2 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 O2 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. © 2009 IOP Publishing Ltd.
  • A. Kouchi, Y. Oba, N. Miyauchi, H. Hidaka, N. Watanabe
    Cryobiology Elsevier {BV} 59 (3) 370  2009 [Refereed][Not invited]
  • 大場 康弘, 宮内 直弥, 千貝 健, 日高 宏, 渡部 直樹, 香内 晃
    日本惑星科学会秋期講演会予稿集 日本惑星科学会 2008 (0) 2008/11 [Not refereed][Not invited]
  • H. Hidaka, N. Miyauchi, A. Kouchi, N. Watanabe
    Chemical Physics Letters 456 (1-3) 36 - 40 0009-2614 2008/04/21 [Refereed][Not invited]
     
    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. © 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 0009-2614 2008/04 [Refereed][Not invited]
     
    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.
  • 分子雲で生じる低温表面反応:表面実験で探る分子進化
    日高宏, 渡部直樹, 香内晃
    低温科学 66 13  2008 [Refereed][Not invited]
  • 渡部直樹, 香内晃, 毛利織絵, 長岡明宏, 日高宏
    The Journaal of the Vacuum Society of Japan 50 (4) 282 - 290 0559-8516 2007 [Refereed][Not invited]
  • H. Hidaka, A. Kouchi, N. Watanabe
    Journal of Chemical Physics 126 (20) 204707  0021-9606 2007 [Refereed][Not invited]
     
    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 H2 O ice, and CO- H2 O 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 H2 O ice and CO- H2 O mixed ice were observed to proceed even at 20 K. This indicates that the coexistence of H2 O 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 kD kH 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 kD kH and by a model calculation of the potential tunneling with the asymmetric Eckart potential. © 2007 American Institute of Physics.
  • N. Watanabe, A. Nagaoka, H. Hidaka, T. Shiraki, T. Chigai, A. Kouchi
    PLANETARY AND SPACE SCIENCE 54 (11) 1107 - 1114 0032-0633 2006/09 [Refereed][Not invited]
     
    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.
  • 星間塵表面での低温水素原子反応による分子進化
    渡部直樹, 長岡明宏, 日高宏, 香内晃
    固体物理 特集号 <新しい水素の科学> 41 (1) 59 - 68 2006 [Refereed][Not invited]
  • 星間塵表面での低温水素原子反応による分子進化
    渡部直樹, 長岡明宏, 日高宏, 香内晃
    固体物理11 41 755 - 764 2006 [Refereed][Not invited]
  • Naoki Watanabe, Hiroshi Hidaka, Akira Kouchi
    AIP Conference Proceedings 855 122 - 127 0094-243X 2006 [Refereed][Not invited]
     
    Using cold atomic hydrogen and deuterium beams, hydrogenation and deuteration of solid CO on the surface of H2O ice were investigated in the surface-temperature range 8-20 K. In hydrogenation experiments, formaldehyde and methanol were produced efficiently by successive hydrogenation of CO below 20 K in conditions similar to those in molecular clouds. In deuteration experiments, we found, for the first time, that D2CO and CD3OD are formed from CO, with the reaction proceeding similarly to hydrogenation although at a much slower rate. From the attenuation curve of the parent CO at 15 K, the relative reaction rate of CO-deuteration to -hydrogenation was determined to be about 0.1. This isotope effect is considered to be due to tunneling reaction. © 2006 American Institute of Physics.
  • Hiroshi Hidaka, Naoki Watanabe, Akira Kouchi
    AIP Conference Proceedings 855 107 - 112 0094-243X 2006 [Refereed][Not invited]
     
    The reaction of cold H and D atoms with solid formaldehyde (D2CO and H2CO) deposited on amorphous H2O ice at 15 K was studied experimentally by in-situ FTIR spectroscopy. New routes of formation of deuterated formaldehyde (HDCO and D2CO) were identified. In the reaction of D atoms with H2CO, H-D substitution was observed, H 2CO → HDCO → D2CO, and for the reaction of H atoms with D2CO, the analogous D-H substitution was observed, D 2CO → HDCO → H2CO. In the reaction of D atoms with H2CO, the rate of H-D substitution was greater than that of formation of deuterated methanol-d2-4 by addition of 2D atoms to formaldehyde-d0-2. However, in the reaction of H atoms with D 2CO, the rate of D-H substitution was comparable to that of addition of 2H atoms to D2CO. © 2006 American Institute of Physics.
  • 星間塵表面反応による星間分子の重水素濃集メカニズム
    渡部直樹, 長岡明宏, 日高宏, 香内晃
    日本惑星科学会誌 14 175 - 182 2005 [Refereed][Not invited]
  • H Hidaka, N Watanabe, T Shiraki, A Nagaoka, A Kouchi
    ASTROPHYSICAL JOURNAL 614 (2) 1124 - 1131 0004-637X 2004/10 [Refereed][Not invited]
     
    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.
  • 星間塵表面反応による有機分子生成および重水素濃集機構
    渡部直樹, 香内晃, 白木隆裕, 長岡明宏, 日高宏
    日本惑星科学会誌 13 226 - 232 2004 [Refereed][Not invited]
  • Influence of ice composition on the formation on interstellar formaldehyde and methanol on dust grains
    A. Nagaoka, N. Watanabe, T. Shiraki, H. Hidaka, A. Kouchi
    Proceedings of the 37th isas luna and planetary symposium 4 91 - 94 2004 [Refereed][Not invited]
  • H Hidaka, S Jinno, H Tanuma, N Kobayashi
    JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS 36 (8) 1515 - 1524 0953-4075 2003/04 [Refereed][Not invited]
     
    The mobility of NO+ in helium has been measured at 77 and 4.3 K using a very low temperature drift tube mass spectrometer. The dependence of mobility on the reduced electric field E/N at 77 K is similar to that of rare-gas ions in helium at 82 K. The mobility measured at 4.3 K reaches a maximum at an effective temperature around 450 K and a minimum around 15 K. Below 100 K the mobility is lower than the polarization limit, which is given by the longrange polarization interaction between the ion and the neutral atom or molecule. As possible reasons for this phenomenon, the clustering reaction, the rotational excitation by the collision and the attractive r(-6) term in the interaction potential are discussed.
  • Molecular ion mobility in helium gas at very low temperature
    H. Hidaka, S. Matoba, S. Jinno, H. Tanuma, N. Kobayashi
    Atomic collision research in japan -Progress report- 28 18 - 19 2002 [Refereed][Not invited]
  • H Tanuma, H Hidaka, N Kobayashi
    PHYSICS OF ELECTRONIC AND ATOMIC COLLISIONS 500 699 - 703 0094-243X 2000 [Refereed][Not invited]
     
    Doubly charged helium cluster ions Kr2+-He-n (n less than or equal to 40) have been produced when Kr2+ ions are injected into helium gas cooled by liquid helium. Magic numbers n = 12 and 32 have been observed in the size distribution of these cluster ions. These magic numbers suggest the shell structure in which an icosahedron consisting of twelve helium atoms performs as a core in the cluster ion. Not only the clustering, charge transfer between Kr2+ and He also takes place as a competitive reaction of the cluster formation. Behavior of each electronic states of the incident ions in collisions with helium have been discussed on a crude potential crossing model.

Conference Activities & Talks

  • Reactive desorption of methanol from amorphous solid water at 10K  [Invited]
    HIDAKA Hiroshi
    Cosmic dust 2019  2019/08
  • Tunneling chamical reactions on low-temperature interstellar grain surfaces  [Invited]
    日髙 宏
    One-day symposium on E-ring based molecular science  2013/02
  • Formation of deuterated formaldehyde on low temperature surface: isotope effect of quantum tunneling reactions  [Invited]
    日髙 宏
    ASTROCHEM2012  2012
  • Formation routes of deuterated formaldehyde and methanol by tunneling reaction on amorphous solid water at 10-20K  [Invited]
    日髙 宏
    COSPAR2012  2012
  • 低温氷表面での水素原子反応における氷構造の影響-アモルファスと結晶の比較-  [Invited]
    日髙 宏
    水素量子アトミクス 第6回研究会  2007/12

MISC

Research Grants & Projects

  • 分子雲における氷・有機物生成
    文部科学省: 科学研究補助金(新学術領域研究(研究領域提案型))
    Date (from‐to) : 2013/06 -2018/03 
    Author : 香内 晃
  • 星間塵表面での分子進化と新しい同位体分別機構
    文部科学省: 科学研究補助金(基盤研究(S))
    Date (from‐to) : 2012/05 -2017/03 
    Author : 渡部 直樹
  • 極低温原子間力顕微鏡によるアモルファス氷の表面構造および表面電位の解明
    文部科学省: 科学研究補助金(基盤研究(C))
    Date (from‐to) : 2014/05 -2016/03 
    Author : 日髙 宏
  • 氷生成過程のその場観察・構造解析のための極低温超高真空透過型電子顕微鏡の開発
    文部科学省: 科学研究補助金(基盤研究(A))
    Date (from‐to) : 2013/10 -2016/03 
    Author : 香内 晃
  • 文部科学省:科学研究費補助金(若手研究(B))
    Date (from‐to) : 2012 -2012 
    Author : 日高 宏
  • 文部科学省:科学研究費補助金(基盤研究(B))
    Date (from‐to) : 2010 -2012 
    Author : 香内 晃, 渡部 直樹, 日高 宏
     
    星間分子雲で起こっている表面原子反応による分子生成は,下地(基板)であるアモルファス氷の存在によって,反応速度が大きくなることが明らかになっている.しかし,アモルファス氷の表面構造は全く明らかになっておらず,その構造解明が急がれる.本研究計画では,超高真空原子間力顕微鏡(AFM)の冷却システムを開発し,アモルファス氷の表面構造を観察する.並行して,反応速度論的データを取得し,双方の情報を用いることにより,極低温表面原子反応においてアモルファス氷が持つ触媒的効果の実体を解明する.これによって,分子雲での分子進化の全容解明に迫る.本年度は,以下の研究を実施した.現有のAFMの試料(サファイヤ基板)を冷却するために,液体ヘリウムクライオスタットを製作した.また,アモルファス氷を作製するためには,AFMに水蒸気を導入する必要があり,このために,ガス導入系およびガス混合装置を作製した.来年度以降は,これらの装置をAFMに取り付け,種々の方法で作製したアモルファス氷の表面構造を分子レベルで観察する予定である.現有の極低温表面原子反応実験装置を用いて,極低温表面原子反応の速度論的データを取得した.水素原子のアモルファス氷表面での拡散係数の測定にあたっては,購入したエキシマレーザーを用いて吸着原子を脱離させ,それを現有の飛行時間型質量分析計で分析した.それらのデータから,水素原子の付着係数お...
  • 文部科学省:科学研究費補助金(新学術領域研究(研究課題提案型))
    Date (from‐to) : 2009 -2011 
    Author : 渡部 直樹, 日高 宏
     
    本年度は,研究課題の主要な目的のひとつである,低温(アモルファス)氷表面での水素原子拡散の同位体効果および,水素原子再結合反応により生成した水素分子の原子核スピン温度の測定を行った.氷表面に存在する(重)水素原子をレーザー誘起脱離させたのちREMPI法により直接検出し,その強度の時間減衰(再結合による水素分子生成により引き起こされる)から表面拡散の情報の得た.その結果,表面温度8Kでは水素と重水素原子の間で拡散の速さに大きな違いは見られず,拡散はトンネル効果によるものではなく,アレニウス的なものであることが示唆された.このことは,表面再結合による水素分子の生成速度には同位体効果がほとんど現れないであろうことを意味する.再結合により生成した水素分子のスピン温度を測定したところ,およそ200K以上を示す高温平衡値3に近いことがわかった.また,生成した水素分子はアモルファス氷表面で再トラップされた後に,スピン温度が時間とともに下がる(オルソ→パラ転換する)事がわかった.この結果は,星間水素分子のスピン温度が温度領域により異なるという天文観値をうまく説明することができる.有機分子CH_3NH_2(メチルアミン)に関して,氷表面原子トンネル反応による重水素濃集が起こるか予備実験を行ったところ,HがDに置換する反応だけではなく,その逆のDがH置換するプロセスも進むことが分かった.
  • 文部科学省:科学研究費補助金(基盤研究(C))
    Date (from‐to) : 2009 -2011 
    Author : 渡部 直樹, 日高 宏
     
    本研究の目的は水分子の重水素濃集に対する星間塵表面反応の寄与を実験により定量化することである.本年度は水分子生成プロセスのひとつとして考えられるOHラジカルと水素,重水素分子の反応について調べた.反応物がすべて水素の場合,反応式はOH+H_2→H_2O+Hである.この反応は発熱で,気相では3000K相当の活性化エネルギーを持つ.そのため,低温氷表面ではトンネル反応による同位体効果が期待される.H_2OもしくはD_2Oガスをマイクロ波放電で解離しOH(OD)ラジカルを生成した.このときのガスの解離率はおよそ80%以上であると見積もられた.ODラジカルとH_2ガス,OHラジカルとD_2ガスをそれぞれ10Kの低温基板に蒸着したところ,前者ではHDO固体の生成が確認されたが,後者では生成されなかった.この結果はOD+H_2→HDO+Hが進む一方でOH+D_2→HDO+Dが起こらないことを示している.両反応には活性化エネルギーに大きな違いはないため,反応の有無は反応の実効質量(effective mass)の違いがもたらすトンネル反応の同位体効果によるものと考えられる.実際の宇宙空間ではD_2の存在量は多くない.今後の実験で,OH+HD→HDO+Hを調べることにより,この反応系が星間水分子の重水素濃集に寄与し得るかを確認する.
  • Ministry of Education, Culture, Sports, Science and Technology:Grants-in-Aid for Scientific Research(若手研究(B))
    Date (from‐to) : 2007 -2008 
    Author : Hiroshi HIDAKA
     
    極低温星間塵表面上で生成・脱離した水素分子の反応熱分配過程を実験的に明らかにするため,低温基板表面で水素原子の結合反応により水素分子を生成し,脱離した水素分子の運動・振動・回転エネルギー分布を測定する実験装置を構築した.
  • Ministry of Education, Culture, Sports, Science and Technology:Grants-in-Aid for Scientific Research(基盤研究(B))
    Date (from‐to) : 2007 -2008 
    Author : Naoki WATANABE, HIROSHI HIDAKA
     
    星間分子の重水素濃集プロセスとして研究代表者らが提唱している極低温星間塵表面反応を, 実験により定量的に評価した. 特に, 高度な重水素濃集が観測で確認されているホルムアルデヒド, メタノールの重水素化表面反応に焦点をあて, 重要な反応経路について実効的な反応速度定数を決定し, 上記分子種に関する重水素濃集の星間塵表面反応ネットワークを完成させた.


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