Structure and physical properties of impure amorphous interstellar icy grains

不纯非晶星际冰晶粒的结构和物理性质

• 批准号: 09304050
• 负责人: AKIRA Kouichi
• 金额: $ 24.64万
• 依托单位: HOKKAIDO UNIVERSITY
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (A)
• 财政年份: 1997
• 资助国家: 日本
• 起止时间: 1997 至 1999
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-09304050/
• 关键词: amorphous ice; fine particles; low temperature; atomic force microscope; structure; comet; アモロフォス氷

The following research was carried out on the formation and metamorphism of amorphous icy grains and origin and evolution of comets using newly developed ultrahigh-vacuum very low temperature atomic force microscope and existing equipments :1) By irradiating the ultraviolet rays onto amorphous ice thin film, we analyze the formation of hydrogen molecule quantitatively. In addition, the reaction cross section was measured, and the reaction mechanism was decided.2) The measurements on physical properties of impure amorphous ices were carried out. The thermal conductivity of impure amorphous ice was found to be 2-3 orders of magnitude smaller than that of the amorphous ice without the defect. As a result of the differential thermal analysis, we found that the crystallization of amorphous ices including impurities were endothermic reaction.3) There results clearly shows that the some properties of impure amorphous ices strongly depends on their defect structure in amorphous ices.4) On the basis of the above results, we have calculated the thermal history of comet nucleus. We found that runaway crystallization considered until now could not be occurred in the actual comet nucleus.

利用新研制的超高真空极低温原子力显微镜和现有设备，对非晶冰粒的形成和变质以及彗星的起源和演化进行了如下研究：1）通过紫外线照射非晶冰薄膜，定量分析氢分子的形成。此外，还测量了反应截面，并对反应机理进行了判断。2）对不纯非晶冰的物理性质进行了测量。发现不纯的非晶冰的热导率比没有缺陷的非晶冰的热导率小2-3个数量级。差热分析结果表明，含杂质的非晶冰的晶化是吸热反应; 3）结果表明，杂质非晶冰的某些性质与其缺陷结构密切相关; 4）在此基础上，计算了彗星核的热历史。我们发现到目前为止所认为的失控结晶在实际的彗核中是不可能发生的。

项目成果

Kouchi, A., et al.: "Crystallization Heat of Impure Amorphous H_20 Ice"Geophys. Res. Lett. in press

Kouchi, A. 等人：“不纯非晶态 H_20 冰的结晶热”Geophys。

Kouchi A.et al.: "Crystallization Heat of Impure Amorphous H2O Ice"Geophys.Res.Lett.. (in press).

Kouchi A.et al.：“不纯非晶 H2O 冰的结晶热”Geophys.Res.Lett..（出版中）。

Sugi, N., M.Arakawa, A.Kouchi and N.Maeno: "In-situ mass spectrometric observation of impact vaporization of water-ice at low temperatures" Geophys.Res.Lett.25. 837-840 (1998)

Sugi, N.、M.Arakawa、A.Kouchi 和 N.Maeno：“低温下水冰冲击汽化的原位质谱观测”Geophys.Res.Lett.25。

Jenniskens P, Blake D.F. and Kouchi A.: "Amorphous water ice:a solar system material." Solar System Ices. 139-155 (1998)

詹尼斯肯斯 P、布莱克 D.F.

Kouchi A.et al.: "New methods for making amorphous icy grains for comet nucleus simulation experiments"Proc.32nd ISAS Lunar and Planetary Symp.. 121-124 (1999)

Kouchi A.等人：“为彗星核模拟实验制作非晶冰粒的新方法”Proc.32nd ISAS Lunar and Planetary Symp.. 121-124 (1999)