Study of evaporative-cooling and freezing processes of liquid droplets in vacuum by developing spectroscopic approach to temperature measurement

2019 Fiscal Year Final Research Report

• Project/Area Number: 17K19107
• Research Category: Grant-in-Aid for Challenging Research (Exploratory)
• Allocation Type: Multi-year Fund
• Research Field: Physical chemistry, Functional solid state chemistry, and related fields
• Research Institution: Kyushu University
• Principal Investigator: Terasaki Akira 九州大学, 理学研究院, 教授 (60222147)
• Project Period (FY): 2017-06-30 – 2020-03-31
• Keywords: 液滴 / 水 / 蒸発冷却 / ラマン散乱 / 温度評価

Outline of Final Research Achievements

A liquid in a vacuum has been a challenging object of physical chemistry because it generally freezes rapidly via fast evaporative cooling. We tackled this issue on water by our own experimental technique dealing with micro-droplets. We succeeded in systematic measurement of time for freezing, which takes place in a millisecond time scale, as a function of droplet size. Numerical simulation of these experimental results revealed that water droplets get frozen at a deeply supercooled temperature and that homogeneous nucleation rates of water are evaluated in such a low-temperature regime, which has been under debate. These achievements would initiate novel chemistry of liquids in a vacuum.

Free Research Field

物理化学

Academic Significance and Societal Importance of the Research Achievements

液体の中でも特に関心が持たれる水を取り上げ、その過冷却状態の熱力学過程の実験研究を従来よりも低温の新たな温度領域にまで推し進めた。その結果、水の凍結核生成速度について大気化学分野の従来からの議論に新たな知見を加えたほか、宇宙空間での水の挙動について惑星科学の視点からも注目が寄せられるなど、本研究成果は広い波及性を持ち、高い学術的意義を示している。また、水は自然界に遍在し、生体内等でも重要な液体であることから、社会的な意義も大きい。