Line shape analysis of the depolarized Rayleigh spectra of CS2/PS mixtures

The relaxation dynamics of carbon disulfide are investigated in mixtures with polystyrene (PS) using the time-resolved optical heterodyne-detected optical Kerr effect (OHD-OKE). The data are analyzed using both the model-dependent approach, which assumes four distinct temporal responses, and the model-independent Fourier transform approach, which generates a spectral response that can be compared with results obtained by depolarized Rayleigh scattering. A slow dynamics is observed for the OHD-OKE transient decaying exponentially with a time constant that varies from 1.68 ps for neat CS2 to 3.76 ps for the most concentrated CS2PS mixture. The increase of this time constant accompanies an increase in the viscosity of the mixture, so we can associate this component with the diffusive reorientation process of the induced polarizability anisotropy of the carbon disulfide in the mixture. The short-time nuclear response is characterized in the frequency domain by a broad band that peaks around 30 cm(-1) for neat carbon disulfide, and is associated with a complex relaxation pattern. The vibrational distribution shifts to higher frequencies when the PS concentration is increased in the mixture. This result is discussed in terms of an increase in the interaction strength between the PS phenyl rings and the carbon disulfide molecules.

Section: ͑4͒supporting

confidence: 88%

Section: ͑4͒mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Time-resolved optical Kerr-effect investigation on CS2/polystyrene mixtures

Heisler

Correia

Buckup

et al. 2005

“…the distance between the centers of mass obtained was around 3.2 Å. 32 These results were also obtained by da Silveira et al, 33,34 in which they realized an ab initio calculation on C 6 H 6¯C S 2 cluster to determine the stabilization energies and the preferential configurations between the CS 2 -C 6 H 6 pair in this van der Waals complex. In that work, the authors also calculated the electronic density of the molecules CS 2 and C 6 H 6 when they were in the energy minimization configuration, establishing charge transfers between these molecules for all stable configurations.…”

Section: Resultssupporting

confidence: 68%

Molecular dynamics investigation with the time resolved optical Kerr effect on the CS2–C6H6 mixtures

Heisler

Correia

Cunha

2006

An investigation of the molecular dynamics in pure liquids and in mixtures through the technique of time resolved optical Kerr effect is performed. The samples studied were the mixtures of carbon disulfide (CS(2)) with benzene (C(6)H(6)). The molecular dynamics of the pure liquids is briefly discussed while the main results are obtained for the mixtures. A slow dynamics component is observed for the optical heterodyne detected optical Kerr effect transient decaying exponentially with time constants on picosecond time scale. The fast subpicosend time relaxations are analyzed in terms of the nondiffusive component of the spectral response that is associated with the molecular dynamics. The modifications of the spectrum are quantified, and the explanation of the observed changes is given in terms of the structural interaction configurations that produced changes in the intermolecular potential within which the molecules execute librational motions.

“…Traditionally, the dynamics of atomic and molecular liquids are studied by far-infrared ͑FIR͒ absorption spectroscopy 3,4 or by Rayleigh-Raman scattering, [5][6][7][8] that measure the Fourier transform of the one-time correlation function of the dipole moment and polarizability, respectively. In the thermal range below 300 cm Ϫ1 , the fluctuations in these bulk properties are associated with the same lowfrequency intermolecular motions.…”

Section: Introductionmentioning

confidence: 99%

Time resolved four- and six-wave mixing in liquids. I. Theory

Steffen¹,

Fourkas

Duppen

1996

155

154

Low-frequency intermolecular dynamics in liquids is studied by ultrafast four-and six-wave mixing. The theory of these nonlinear optical processes is given for electronically nonresonant optical interactions up to fifth order in the electric field. The Born-Oppenheimer approximation is used to separate the motional part of the response functions from coordinate independent electronic hyperpolarizabilities. A large variety of experiments, involving far-infrared absorption, ordinary Rayleigh-Raman or hyper Rayleigh-Raman scattering is covered by this theory. The response in nonresonant six-wave mixing comprises four dynamically different processes. It is shown that one of the terms contains information on the time scale͑s͒ of intermolecular dynamics, that is not available from lower-order nonresonant experiments. For instance, homogenous and inhomogeneous contributions to line broadening can be distinguished. The optical response of harmonic nuclear motion is calculated for nonlinear coordinate dependence of the polarizabilities. Results for level-dependent and level-independent damping of the motion are compared. It is shown that level-dependent damping destroys the interference between different quantum mechanical pathways, yielding an extra contribution to the fifth-order response that has not been discussed before. When two or more nuclear modes determine the optical response, their relative contributions to the four-and six-wave mixing signals are in general different. These contributions are determined by the coordinate dependence of the electronic polarizability, which is usually not fully known. Model calculations are presented for the dynamic parameters of liquid CS 2. The theory of this paper will be employed in Part II, to analyze experimental results on femtosecond four-and six-wave mixing.