Development of time-and space-resolved low frequency Raman spectroscopy and elucidation of melting processes of ionic liquids

我们开发了一种新的低频拉曼光谱来解释离子液体的熔化过程。它可以快速和同时监测熔化的各个方面：温度的升高，晶格振动的损失和分子内结构的变化。发现了几个新现象：(1)在高于熔点的温度下存在瞬态结晶状态；(2)熔化过程中分子内构象变化的延迟；(3)离子液体中阴离子和阳离子的热不平衡。第三个结果将导致一个新的概念，“分子温度”，这是有用的讨论一般液体和离子液体的热不均匀性。

We developed a new low frequency Raman spectroscopy for elucidating melting processes of ionic liquids. It enables fast and simultaneous monitoring of various aspects of melting : increase of temperatures, loss of lattice vibrations, and intramolecular structure change. Several new phenomena are found,(1) a transient crystalline state existing at temperatures higher than the melting point,(2) delay of intramolecular conformational changes during the melting, and(3) thermal non-equilibration of anions and cations in an ionic liquid. The third result will lead to a new concept,"molecular temperature", which is useful for discussing thermal inhomogeneity of general liquids as well as ionic liquids.