Locally Ordered Structures in Molecular Liquids Revealed with Femtosecond Fourier-Transform Raman Spectroscopy

Lotshaw, William T.; Staver, P. Randall; McMorrow, D.; Thantu, Napoleon; Melinger, Joseph S.

doi:10.1007/978-3-642-85176-6_25

Cited by 9 publications

(11 citation statements)

References 2 publications

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“…For example, the dip in the middle is gone and the spectrum now falls off more rapidly on the low-frequency side than in the spectra of either neat biphenyl or neat n -heptane. Similar behavior is observed when benzene is diluted in CCl 4 . These changes indicate that the spectrum of the mixture cannot be simply regarded as a linear superposition of the spectra of the neat liquids but reflects the dynamics of biphenyl in solution.…”

Section: Resultssupporting

confidence: 54%

“…The spectra are typically fit by line shape functions composed of a low-frequency component and a high-frequency component. ,− It has been suggested that the low-frequency shoulder of benzene is associated with the modes of locally ordered structures or clusters . The observation that the low-frequency shoulder is reduced upon dilution in a weakly interacting solvent lends credence to this argument . Chelli et al. , and Ratajska-Gadomska et al , have taken this point of view a step further by assuming that the liquid is organized in instantaneous quasi-crystalline short-range clusters and simulating the spectrum of benzene by using the phonon modes within these clusters.…”

Section: Introductionmentioning

confidence: 99%

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Intermolecular Spectrum of Liquid Biphenyl Studied by Optical Kerr Effect Spectroscopy

2004

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The intermolecular spectra of neat liquid biphenyl and biphenyl/n-heptane mixtures were obtained by using optically heterodyne detected optical Kerr effect (OHD-OKE) spectroscopy. The intermolecular spectrum of biphenyl is broad and bimodal in character. The spectrum of biphenyl undergoes a red shift and line narrowing with temperature and upon dilution in n-heptane. The spectra can be well fit by a bimodal line shape function. Inconsistencies, however, arise in the interpretation of the effects of temperature and dilution on the individual component bands. The spectrum of biphenyl is similar in frequency and width to that of benzene. Packing models suggest that rotational motion is more hindered in biphenyl than in benzene, which could explain the similarity of the spectra of the two liquids, even though the moments of inertia for the two molecules are quite different.

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Section: Resultssupporting

confidence: 54%

Section: Introductionmentioning

confidence: 99%

Intermolecular Spectrum of Liquid Biphenyl Studied by Optical Kerr Effect Spectroscopy

2004

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“…Intermolecular modes, like their intramolecular counterparts, can shift either to higher or lower frequency, depending on whether the solute−solvent interaction is stronger or weaker than the solute−solute interaction. They can even remain effectively unshifted, as in the case of benzene/CCl 4 solutions . For the present case, CS 2 −CS 2 interactions are mediated by the electrostatic multipole potential. ,, A substantial contribution to the interactions derive from the large permanent quadrupole moments of the CS 2 molecules .…”

Section: Discussionmentioning

confidence: 71%

Analysis of Intermolecular Coordinate Contributions to Third-Order Ultrafast Spectroscopy of Liquids in the Harmonic Oscillator Limit

et al. 2001

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The apparently-multicomponent subpicosecond intermolecular dynamics of carbon disulfide liquid are addressed in a unified manner in terms of an inhomogeneously broadened quantum mechanical harmonic oscillator model for a single vibrational coordinate. For an inhomogeneously broadened (Gaussian) distribution of oscillators, the model predicts naturally the bimodal character of the subpicosecond intermolecular dynamics of carbon disulfide liquid, and also the spectral evolution effects (spectral narrowing and saturation) that are observed for solutions of carbon disulfide in weakly interacting alkane solvents. The unique dynamical signature of these low-frequency vibrational coordinates is determined largely by the physical constraints on the coordinates (near equality of oscillator frequency, dephasing frequency, and inhomogeneous bandwidth), such that constructive and destructive interference effects play a dominant role in shaping the experimental observable.

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“…The size of the CCl 4 contribution can be estimated by normalizing with respect to the intensity of the CCl 4 intramolecular modes at 218 and 314 cm -1 . 70 However, this assumes that the shape of the intermolecular spectral density is independent of dilution. Since the CCl 4 spectral density is largely collision induced this assumption does not seem justified (unless the CCl 4 volume fraction is large).…”

Section: Resultsmentioning

confidence: 99%

Ultrafast Dynamics of Polar Monosubstituted Benzene Liquids Studied by the Femtosecond Optical Kerr Effect

2000

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The femtosecond and picosecond dynamics of liquid aniline, nitrobenzene, and benzonitrile have been recorded through measurements of the optically heterodyne detected optical Kerr effect. A major part of the subpicosecond dynamics is assigned to librational motion. This assignment is supported by studies of para-substituted benzonitrile derivatives with differing moments of inertia. The librational frequencies of the three liquids are only weakly dependent on temperature but shift to lower frequency on dilution in inert solvents. The picosecond relaxation dynamics are well described by a biexponential function. The slowest relaxation time behaves, at least qualitatively, as predicted by hydrodynamic models of orientational diffusion. However, quantitative analysis suggests that some of the assumptions concerning the molecular shape or hydrodynamic boundary condition are inadequate to completely describe diffusive orientational motion in these liquids. Measurements of the slowest relaxation time as a function of dilution in nonpolar solvent showed that static orientational pair correlation is negligible in these liquids. The faster of the two picosecond exponential relaxation times could not be ascribed to orientational diffusion, and is instead proposed to arise from structural relaxation occurring on the picosecond time scale in these liquids.

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Locally Ordered Structures in Molecular Liquids Revealed with Femtosecond Fourier-Transform Raman Spectroscopy

Cited by 9 publications

References 2 publications

Intermolecular Spectrum of Liquid Biphenyl Studied by Optical Kerr Effect Spectroscopy

Intermolecular Spectrum of Liquid Biphenyl Studied by Optical Kerr Effect Spectroscopy

Analysis of Intermolecular Coordinate Contributions to Third-Order Ultrafast Spectroscopy of Liquids in the Harmonic Oscillator Limit

Ultrafast Dynamics of Polar Monosubstituted Benzene Liquids Studied by the Femtosecond Optical Kerr Effect

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