Local density inhomogeneities detected by Raman scattering in supercritical hexafluorobenzene

Abstract: The influence of the local density inhomogeneities in supercritical hexafluorobenzene C 6 F 6 has been assessed using Raman spectroscopy. The polarized and depolarized profiles associated with the ν 1 (A 1g ) "breathing" mode of the molecule has been analyzed for the fluid in a wide density range (0.1 ≤ ρ* = ρ/ρ C ≤ 3), namely under isothermal conditions (T* = T/T C~ 1.11 and close to the critical isotherm T*~1.02). 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/ρ C ≤ 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 τ 2R 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

Breaking the Structure of Liquid Hydrogenated Alcohols Using Perfluorinated tert -Butanol: A Multitechnique Approach (Infrared, Raman, and X-ray Scattering) Analyzed by DFT and Molecular Dynamics Calculations

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The structure of concentrated aqueous solutions of chromium nitrate and cerium chloride studied by X-ray diffraction and Raman spectroscopy

Concentrated aqueous solutions of chromium nitrate and cerium chloride were investigated by X-ray diffraction and Raman spectroscopy. The X-ray diffraction patterns of two sets of solutions (1.60 up to 2.48 mol dm- 3 for chromium nitrate and 0.98 up to 2.81 mol dm- 3 for cerium chloride) display an intense maximum, prepeak, in the angular region about Q0 ~ 0.9 Å- 1 (Q = 4 [pi] sin [theta] / [lambda], [theta] being the diffracting angle). The value of Q0 corresponding to these maxima is proportional to the power 1/3 of the molar concentration. The proportionality coefficient has the value that should be observed for a close packing (fcc network) if assumed for cations. This study demonstrates, once more, the existence of an intermediate range order (up to ~ 10 Å) in very concentrated aqueous solutions of salts constituted by small ions of different valences, range order previously reported by these authors in many articles. Raman experiments are in consonance with X-ray diffraction results.http://www.sciencedirect.com/science/article/B6TGR-4PGY4JV-1/1/bc6475c0d11944c50e37a2cf97406a0