Low-frequency Raman, also known as terahertz-Raman (THz-Raman), spectroscopy offers a laboratory benchtop-based alternative to synchrotron X-ray diffraction for real-time, in situ monitoring of ball-milling mechanochemical reactions. Although direct monitoring of the long-range structure of materials during mechanochemical reactions is generally challenging by conventional Raman spectroscopy, and typically requires synchrotron X-ray diffraction, here we use THz-Raman spectroscopy to monitor mechanosynthesis of cocrystals, stoichiomorphs, and polymorphs, detect multi-step sequences, and discover solid-state phases in systems difficult to differentiate using fingerprint-region Raman spectroscopy—all through real-time observation of changes in lattice vibrational models. The methodology is augmented by periodic density functional theory (DFT), which enables structural interpretation of spectroscopic changes, notably the identification of THz-Raman bands associated with halogen bond transformations. Simultaneous monitoring of mechanochemical processes in both the fingerprint and low-frequency Raman regions enables real-time observation of changes to extended as well as molecular structure during milling, in a single laboratory benchtop experiment, without synchrotron radiation.

中文翻译：

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太赫兹-拉曼光谱，用于在研磨机械化学中对扩展的超分子结构变化进行原位台式监测


低频拉曼光谱，也称为太赫兹拉曼 （THz-Raman），为同步辐射 X 射线衍射提供了一种基于实验室台式的替代方案，用于实时、原位监测球磨机械化学反应。尽管传统拉曼光谱通常难以在机械化学反应过程中直接监测材料的长程结构，并且通常需要同步加速器 X 射线衍射，但在这里，我们使用太赫兹拉曼光谱来监测共晶、化学晶型和多晶型物的机械合成，检测多步骤序列，并发现系统中难以使用指纹区域拉曼光谱区分的固态相——所有这些都是通过实时进行的观察晶格振动模型的变化。该方法通过周期密度泛函理论 （DFT） 得到增强，该理论能够对光谱变化进行结构解释，特别是识别与卤素键转变相关的太赫兹拉曼带。同时监测指纹和低频拉曼区域的机械化学过程，可以在单个实验室台式实验中实时观察研磨过程中延伸和分子结构的变化，而无需同步辐射。