アモルフな水氷における構造的移行と天体物理学的影響
1NASA/Ames Research Center, Moffett Field, CA 94035, USA.
まとめ
水氷は,温暖化中に3つの無形形態 (Iah, Ial, Iar) を経由して変化する構造的変化を経験します. これらの変換は,天体物理学上の氷に観察された異常な性質を説明します.
科学分野:
- マテリアルサイエンス 材料科学
- アストロケミストリー アストロケミストリー
- 物理化学 物理化学
背景:
- アモルフな水氷は,天体物理的な環境で一般的です.
- その構造的移行を理解することは,星間氷の観測を解釈する上で極めて重要です.
研究 の 目的:
- 温暖化時に真空下で蒸気で堆積した水氷の構造変化を調査する.
- 水氷の異なる無形な段階とその移行温度を特定し,特徴づけること.
主な方法:
- 構造変化をモニタリングするために,選択領域電子 difraktion (SAED) が採用されました.
- 蒸気で堆積した水氷は,真空下で15Kから188Kまで加熱された.
主要な成果:
- 3つの異なる無形水氷の形が特定されました:高密度無形氷 (Iah),低密度無形氷 (Ial),そして第三の形 (Iar).
- 移行は特定の温度帯で発生した: Iah から Ial (3868 K),そして Iar の形成は 131 K.
- 氷は148Kから少なくとも188Kまでの氷の立方体 (Ic) と共存します.
結論:
- 特定された無形氷の変形は,天体物理的な氷の異常な性質の説明を提供します.
- 岩から岩への移行は,恒星間氷の急性拡散と再結合に関連しています.
- Iar段階は,高温の水分豊富な氷の中で異常なガスの保持と放出を説明する.
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