Local density inhomogeneities detected by Raman scattering in supercritical hexafluorobenzene
Local density inhomogeneities detected by Raman scattering in supercritical hexafluorobenzene
复制标题
通过拉曼散射检测超临界六氟苯中的局部密度不均匀性
DOI：
10.1351/pac200476010141
复制
发表时间：
2004
影响因子：
1.8
通讯作者：
Y. Danten
中科院分区：
文献类型：
--
作者：
M. I. Cabaço;M. Besnard;T. Tassaing;Y. Danten
摘要利用拉曼光谱研究了超临界六氟苯C6F6中局部密度不均匀性的影响。在较宽的密度范围内，即在等温条件下，分析了与分子“呼吸”模式相关的极化和去极化分布。在近临界等温线上，各向同性剖面带中心位置随密度的变化表现出反常的特征，在密度范围（0.6 < ρ* = ρ/ρ c < 1.3）出现高原，而在T* ~ 1.11等温线上则没有。将其解释为由于局部密度不均匀性的存在，并对密度增强因子进行了评价。分子主对称轴的旋转动力学是由扩散过程控制的。两个等温线的旋转相关时间τ2R均表现出异常行为（高原状态）。这些发现证明了纯流体中存在局部密度不均匀性，并表明拉曼光谱很适合研究这些现象。
Abstract The influence of the local density inhomogeneities in supercritical hexafluorobenzene C6F6 has been assessed using Raman spectroscopy. The polarized and depolarized profiles associated with the "breathing" mode of the molecule has been analyzed for the fluid in a wide density range, namely under isothermal conditions. The evolution upon the density of the band center position of the isotropic profile along the near-critical isotherm showed an anomalous behavior, characterized by a plateau in the density range (0.6 < ρ* = ρ/ρC < 1.3), which is not observed along the isotherm T* ~ 1.11. It has been interpreted as due to the existence of local-density inhomogeneities and the density enhancement factor has been evaluated. The rotational dynamics of the main symmetry axis of the molecule is governed by a diffusional process. The rotational correlation time τ2R exhibits an anomalous behavior (plateau regime) for both isotherms. These findings put in evidence the existence of local density inhomogeneities in a pure fluid and show that Raman spectroscopy is well adapted to investigate these phenomena.