A new type of chemical reaction within icy grains

• Project/Area Number: 21H01139
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Basic Section 17010:Space and planetary sciences-related
• Research Institution: Hokkaido University
• Principal Investigator: Masashi Tsuge 北海道大学, 低温科学研究所, 助教 (60454211)
• Project Period (FY): 2021-04-01 – 2024-03-31
• Project Status: Completed (Fiscal Year 2023)
• Budget Amount: ¥18,070,000 (Direct Cost: ¥13,900,000、Indirect Cost: ¥4,170,000); Fiscal Year 2023: ¥1,690,000 (Direct Cost: ¥1,300,000、Indirect Cost: ¥390,000); Fiscal Year 2022: ¥1,820,000 (Direct Cost: ¥1,400,000、Indirect Cost: ¥420,000); Fiscal Year 2021: ¥14,560,000 (Direct Cost: ¥11,200,000、Indirect Cost: ¥3,360,000)
• Keywords: 原子拡散 / 化学進化 / 氷星間塵 / 星間分子雲 / 炭素原子 / 表面拡散 / 水素原子拡散 / 分子進化 / 水素原子反応 / PAH

Outline of Research at the Start

極低温の星間分子雲では、氷で覆われた星間塵（氷星間塵）上での表面反応が分子進化の鍵と考えられ、星間分子生成に関する様々な研究がされてきた。近年、研究代表者らは氷内部における水素原子の活発な化学反応を見いだした。氷内部反応では、これまで考えられていたより高温でも分子生成が可能になるなど、表面反応とは異なる多くの特徴が見られた。本研究ではおもに水素原子を中心に、様々な分子生成に関する氷内部反応を定量的な実験で調べ、反応経路、反応生成物、生成可能温度などの知見を得る。取得された結果をもとに、従来の分子進化モデルへの影響を評価する。

Outline of Final Research Achievements

In the chemical evolution processes occurring within low temperature molecular clouds, it has been demonstrated that chemical reactions on icy grain surface play significant roles. Recently, we found that hydrogen atoms can penetrate into ice mantles and, therefore, they can induce chemical processes without photons and cosmic rays.The aims of this work were as follows: One is to quantify the penetration depths of H-atoms into porous and nonporous amorphous solid water (ASW). The other is to investigate whether atoms other than hydrogen can penetrate into ice or not.
We found that hydrogen atoms penetrate more than 30 nm into porous-ASW and 2-3 nm into nonporous-ASW, where the latter type of ASW is considered relevant to molecular cloud conditions. Carbon atoms were found to diffuse on the surface of ASW at temperatures 20-40 K, indicating that they can penetrate into ASW through cracks.

Academic Significance and Societal Importance of the Research Achievements

星間分子雲内での標準的な化学進化モデルでは、氷表面に吸着する原子種は氷内部における分子生成に影響を与えないとされてきた。我々が見出した「氷内部への原子の侵入」という全く新しい反応プロセスは「光や宇宙線を必要としない氷内部の分子進化プロセス」と言い換えることができ、既存の極低温分子雲における分子進化モデルに大きな変更を要請するという学術的意義を持つ。
本研究で、一部の炭素原子は極低温の条件下でも氷表面を動き回ることを明らかした。本発見は、氷微粒子上で炭素原子が様々な分子種と化学反応を起こし大きな有機分子を生成しうることを示唆しており、宇宙における複雑有機分子形成メカニズムの解明に大きく寄与する。

Research Products

• [Int'l Joint Research] 国立陽明交通大学（台湾）(その他の国・地域)
• [Journal Article] Radical reactions on interstellar icy dust grains: Experimental investigations of elementary processes (2023)
  • Author(s): Tsuge Masashi、Watanabe Naoki
  • Journal Title: Proceedings of the Japan Academy, Series B Volume: 99 Issue: 4 Pages: 103-130
  • DOI: 10.2183/pjab.99.008
  • ISSN: 0386-2208, 1349-2896
  • Year and Date: 2023-04-28
  • Peer Reviewed / Open Access
• [Journal Article] Surface diffusion of carbon atoms as a driver of interstellar organic chemistry (2023)
  • Author(s): Tsuge Masashi, Molpeceres German, Aikawa Yuri, Watanabe Naoki
  • Journal Title: Nature Astronomy Volume: 7 Issue: 11 Pages: 1351-1358
  • DOI: 10.1038/s41550-023-02071-0
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Infrared spectra of isoquinolinium (iso-C9H7NH+) and isoquinolinyl radicals (iso-C9H7NH and 1-, 3-, 4-, 5-, 6-, 7- and 8-iso-HC9H7N) isolated in solid para-hydrogen (2023)
  • Author(s): Joshi Prasad Ramesh、Tsuge Masashi、Tseng Chih-Yu、Lee Yuan-Pern
  • Journal Title: Physical Chemistry Chemical Physics Volume: 25 Issue: 17 Pages: 11934-11950
  • DOI: 10.1039/d3cp00246b
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Penetration of Nonenergetic Hydrogen Atoms into Amorphous Solid Water and their Reaction with Embedded Benzene and Naphthalene (2022)
  • Author(s): Masashi Tsuge, Akira Kouchi, Naoki Watanabe
  • Journal Title: The Astrophysical Journal Volume: 933 Issue: 2 Pages: 138-138
  • DOI: 10.3847/1538-4357/ac752e
  • Peer Reviewed / Open Access
• [Journal Article] Infrared and Laser-Induced Fluorescence Spectra of Sumanene Isolated in Solid para-Hydrogen (2022)
  • Author(s): Weber Isabelle、Tsuge Masashi、Sundararajan Pavithraa、Baba Masaaki、Sakurai Hidehiro、Lee Yuan-Pern
  • Journal Title: The Journal of Physical Chemistry A Volume: 126 Issue: 32 Pages: 5283-5293
  • DOI: 10.1021/acs.jpca.2c02906
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Measurements of ortho-to-para nuclear spin conversion of H2 on low-temperature carbonaceous grain analogs: Diamond-like carbon and graphite (2021)
  • Author(s): Tsuge Masashi、 Kouchi Akira、 Watanabe Naoki
  • Journal Title: The Astrophysical Journal Volume: 923 Issue: 1 Pages: 71-71
  • DOI: 10.3847/1538-4357/ac2a33
  • Peer Reviewed / Open Access
• [Journal Article] Two-Body Metastable Dissociation of <i>n</i>-Pentane and <i>n</i>-Hexane Triplet Dications in Intense Femtosecond-Laser Fields (2021)
  • Author(s): Hoshina Kennosuke、Shirota Tatsuro、Tsuge Masashi
  • Journal Title: The Journal of Physical Chemistry A Volume: 125 Issue: 43 Pages: 9508-9517
  • DOI: 10.1021/acs.jpca.1c06567
  • Peer Reviewed
• [Journal Article] Transmission Electron Microscopy Study of the Morphology of Ices Composed of H2O, CO2, and CO on Refractory Grains (2021)
  • Author(s): Kouchi, A., Tsuge, M., Hama, T., Oba, Y., Okuzumi, S., Sirono, S.-. iti ., Momose, M., Nakatani, N., Furuya, K., Shimonishi, T., Yamazaki, T., Hidaka, H., Kimura, Y., Murata, K.-. ichiro ., Fujita, K., Nakatsubo, S., Tachibana, S., & Watanabe, N.
  • Journal Title: The Astrophysical Journal Volume: 918 Issue: 2 Pages: 45-45
  • DOI: 10.3847/1538-4357/ac0ae6
  • Peer Reviewed / Open Access
• [Presentation] Experimental Investigations on the Behavior of Carbon Atoms on Amorphous Solid Water (2024)
  • Author(s): Tsuge Masashi、Molpeceres German、Aikawa Yuri、Watanabe Naoki
  • Organizer: Laboratory Astrophysics Workshop (ICE 2024)
  • Int'l Joint Research
• [Presentation] Experimental investigations on the behavior of free radicals on the surface of icy grain analogues (2024)
  • Author(s): Tsuge Masashi、Watanabe Naoki
  • Organizer: International Conference on Key Intermediates in Atmospheric Chemistry and Astrochemistry
  • Int'l Joint Research
• [Presentation] Penetration of nonenergetic hydrogen atoms into amorphous solid water and their reactions with embedded molecules (2023)
  • Author(s): Tsuge Masashi、Kouchi Akira、Watanabe Naoki
  • Organizer: 2023 Kavli-IAU Astrochemistry Symposium
  • Int'l Joint Research
• [Presentation] Energy dissipation upon the ortho-to-para conversion of H2 on low temperature interstellar grain surfaces: Amorphous silicate, diamond-like carbon, and amorphous solid water (2023)
  • Author(s): Tsuge Masashi、Kouchi Akira、Watanabe Naoki
  • Organizer: 2023 Kavli-IAU Astrochemistry Symposium
  • Int'l Joint Research
• [Presentation] Diffusive hydrogenation of molecules embedded in amorphous solid water (2022)
  • Author(s): Masashi Tsgue
  • Organizer: Symposium on Next Generation Astrochemistry
  • Int'l Joint Research
• [Presentation] Production of isoquinolinium (iso-C9H7NH+) and isoquinolinyl radical (iso-C9H7NH, 1-iso-HC9H7N, and 3- to 8-iso-HC9H7N in solid para-hydrogen (2022)
  • Author(s): Prasad Ramesh Joshi, Masashi Tsuge, Chih-Yu Tseng, Yuan-Pern Lee
  • Organizer: The 6th Asian Workshop on Molecular Spectroscopy
  • Int'l Joint Research
• [Presentation] 星間塵表面における水素分子のオルソ―パラ転換過程 (2022)
  • Author(s): 柘植雅士、香内晃、渡部直樹
  • Organizer: 第16回分子科学討論会
• [Presentation] Ortho-to-para Nuclear Spin Conversion of H2 on Bare Interstellar Dust Analogs: Amorphous-silicate, Diamond-like Carbon, and Graphite (2022)
  • Author(s): Masashi Tsuge, Akira Kouchi, Naoki Watanabe
  • Organizer: THE 22ND INTERNATIONAL VACUUM CONGRESS
  • Int'l Joint Research
• [Presentation] 模擬星間塵表面における水素分子の核スピン転換過程：表面フォノンによるエネル ギー散逸 (2022)
  • Author(s): 柘植雅士, 香内晃, 渡部直樹
  • Organizer: 原子衝突学会第 47 回年会
• [Presentation] Experimental studies on the behavior of hydrogen on bare grain surfaces and within icy grains (2022)
  • Author(s): Masashi Tsuge
  • Organizer: Chemistry and Physics at Low Temperatures
  • Int'l Joint Research / Invited
• [Presentation] Icy grains are not spherical nor ellipsoidal (2021)
  • Author(s): M. Tsuge, A. Kouchi, T. Hama, Y. Oba, S. Okuzumi, S.-i. Sirono, M. Momose, N. Nakatani, K. Furuya, T. Shimonishi, T. Yamazaki, H. Hidaka, Y. Kimura, K.-i. Murata, S. Tachibana, N. Watanabe
  • Organizer: Workshop on Interstellar Matter
  • Int'l Joint Research / Invited
• [Presentation] Ortho-to-para nuclear spin conversion of H2 on interstellar bare grain analogues (2021)
  • Author(s): M. Tsuge, T. Namiyoshi, K. Furuya, A. Kouchi, N. Watanabe
  • Organizer: Workshop on Interstellar Matter
  • Int'l Joint Research
• [Presentation] Diffusive hydrogenation of CO embedded in amorphous solid water at temperature up to 70 K (2021)
  • Author(s): M. Tsuge, H. Hidaka, A. Kouchi, N. Watanabe
  • Organizer: Workshop on Interstellar Matter
  • Int'l Joint Research
• [Presentation] Experimental studies on the behavior of hydrogen on bare grain surfaces (2021)
  • Author(s): M. Tsuge
  • Organizer: Astrochemical Frontiers
  • Int'l Joint Research / Invited
• [Funded Workshop] The 7th Asian Workshop on Molecular Spectroscopy (2023)