Raman light scattering from supracritical binary fluid mixtures: CH4/CF4

A supracritical fluid mixture of CH4/CF4 (1:9 mole ratio) has been studied at 323 K at densities between 3.0 and 19.1 mol -ℓ (m/ℓ) by inelastic (Raman) light scattering originating from the ν1 totally symmetric stretching mode of methane. Furthermore, a Raman depolarization ratio study of the integr...

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Veröffentlicht in:The Journal of chemical physics 1996-11, Vol.105 (17), p.7285-7293
Hauptverfasser: Baglin, F. G., Sweitzer, S., Stanbery, W.
Format: Artikel
Sprache:eng
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Zusammenfassung:A supracritical fluid mixture of CH4/CF4 (1:9 mole ratio) has been studied at 323 K at densities between 3.0 and 19.1 mol -ℓ (m/ℓ) by inelastic (Raman) light scattering originating from the ν1 totally symmetric stretching mode of methane. Furthermore, a Raman depolarization ratio study of the integrated intensities of the ν1 mode was also carried out as a function of density. A model is proposed to aid in the understanding of the intensity-density behavior in terms of both allowed and interaction-induced (ii) contributions to the overall observed signal. The model makes use of one, two, and three body light scattering via both the dipole polarizability, the dipole–quadrupole polarizability, and also takes into account various partner combinations in the multibody light scattering. Whereas, the model generally predicts correct Iνh behavior, (here I is the Raman intensity and the subscripts refer to the vertical polarization direction of the laser (ν) and the direction of the analyzer either ν or h (horizontal)), it is shown that the standard assumption of the no V–R coupling is violated, leading to a different mechanism for Iiso Raman light scattering. This leads to extensive three-body ii Iiso signal cancellation, but none from the Iνh spectrum. The model adequately explains these concepts through the usual interaction induced processes as well as a unique cross term.
ISSN:0021-9606
1089-7690
DOI:10.1063/1.472599