Real-time investigation on the melting dynamics of aromatic molecular crystals by using fast Low-frequency Raman spectroscopy

结果表明，蒽在熔融过程中存在一种瞬态晶体结构。“过热”晶体的晶格振动，只在熔化过程中才能看到，与稳态的晶格振动不同。我们改进了快速低频拉曼光谱技术，使其能同时监测样品在显微镜下的光学图像。它可以实现亚秒级时间分辨和微米级空间分辨的晶格振动出现（或消失）的跟踪，同时监测形态变化。这将为分子水平上实时跟踪小晶体相变过程中的结构变化提供一种新的方法。

We showed that a transient crystalline structure of anthracene exists in its melting. Lattice vibrations of the'' super-heated'' crystal, which is only seen during the melting, are different to those of the stationary state. We improved the fast low frequency Raman spectroscopy for simultaneous monitoring the optical image of the sample under microscope. It enables sub-second time-resolved and micrometer space-resolved tracing of the appearance(or disappearance) of lattice vibrations with simultaneous monitoring the morphology changes. It will be a new method for molecular-level and real-time tracing structural change of a small crystal during its phase transitions.