Raman spectroscopy is used to study the pressure response of crystalline fluorene up to 9 GPa. Pressures higher than 2.5 GPa cause a reversible rearrangement of the molecular stacking, changes in the electronic properties and structural stiffening, leading to a decrease of the pressure coefficients of the intermolecular peak frequencies. The coefficients are further reduced above 6 GPa where fluorene is fully transformed to its isostructural high-pressure phase, while the coexistence of the two phases is evident in the downstroke spectra. The phase transition has less profound effects on the intramolecular modes with the exception of the C–H vibrations.

中文翻译：

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拉曼光谱研究芴的压力诱导结构相变

拉曼光谱用于研究高达 9 GPa 的结晶芴的压力响应。高于 2.5 GPa 的压力会导致分子堆积的可逆重排、电子性质的变化和结构硬化，导致分子间峰值频率的压力系数降低。在芴完全转化为其同构高压相时，系数进一步降低至 6 GPa 以上，而两相的共存在下冲程光谱中很明显。除了 C-H 振动之外，相变对分子内模式的影响较小。