Study of depolarized Rayleigh scattering in liquid benzene derivatives

The spectrum of the depolarized Rayleigh line has been measured for benzene, toluene, fluorobenzene and bromobenzene (at 22°c). The central part of the spectrum was measured at high resolution using a piezoelectric scanned Fabry-Pérot with a maximum free-spectral range of about 20 cm^-1. The entire spectrum was also measured with a monochromator extending the region to 100 cm^-1. The results from the two techniques were combined in order to deduce the correct line shape from which we were able to determine two relaxation times τ1 and τ2.     

The fine structure of depolarized Rayleigh scattering from liquid acetophenone

The depolarized Rayleigh spectrum I _H ^V of acetophenone exhibits a well-defined doublet structure. The form of this spectrum is analysed using recent microscopic theories (Keyes-Kivelson, Andersen-Pecora) and an older, viscoelastic theory (Rytov). At low temperatures a closer agreement is obtained with the theories of Keyes-Kivelson and Andersen-Pecora.     

Dynamical properties of water-methanol solutions: Brillouin and depolarized Rayleigh scattering

Summary We have performed Brillouin and depolarized Rayleigh light scattering on water-methanol solutions as a function of methanol molar fraction and temperature. For this system, molecular-dynamics (MD) simulation predicts that a shell of water forms around a methanol molecule, prediction which has been recently confirmed by neutron diffraction experiments. The results obtained by light scattering and presented here confirm previous observations and show, in addition, an increase of the stability in time of the water structure in the shells when temperature decreases and methanol concentration approaches a particular value. Paper presented at the I International Conference on Scaling Concepts and Complex Fluids, Copanello, Italy, July 4–8, 1994.     

Intermolecular and diffusive dynamics of pure acetonitrile isotopomers studied by depolarized Rayleigh scattering and femtosecond optical kerr effect

The relaxation dynamics of pure acetonitrile isotopomers has been investigated in the temperature range 8 to 75 ^° C. The overall response of the liquid is measured either recording directly the decay of the optical Kerr signal with heterodyne detection (OHD-OKE) and Fourier transforming the depolarized Rayleigh scattering spectra (DRS). The OHD-OKE signals show a decay that can be described by a bi-exponential law. At some temperatures, stressing to a maximum level the sensitivity of the OHD-OKE experimental set-up, a damped oscillation is observed on top of the fast decay component. The two techniques provide same results with a high level of reproducibility, as far as the slow component is concerned. This latter is described by an exponential law with the time constants ranging in the interval 2.0 to 0.85 ps in the light and approximately in the same interval in the deuterated molecule. The decays are, at all temperatures, well reproduced by the extended diffusion J-model. The fast component, better observed with the OHD-OKE experiments in a restricted temperature range, has time constants ranging from 550 to 350 fs. After the subtraction of the curve due to the slower decay component, the data have also been analyzed by Fourier transforming the fast part of the decay. The spectrum then consists of a broad (approximately 80 cm^-1 wide) band centered at 50 cm^-1. This band is interpreted as the manifestation of intermolecular vibrational motions. Received 21 July 2002 Published online 1st October 2002 RID="a" ID="a"e-mail: foggi@colonnello.lens.unifi.it     

On the depolarized Rayleigh scattering from macromolecular and colloidal solutions — Anisotropy of the diffusional broadening

The width of the depolarized Rayleigh line for the light scattered from a solution of non-spherical particles is calculated from a generalized diffusion equation. Due to the correlation between the translational motion and the orientation of the particles, the diffusional contribution to the width is anisotropic, i.e. the relevant effective diffusion coefficient depends on the scattering angle and on the polarization vectors. This anisotropy is related to the shape of the particles.     

The temperature dependence of the Rayleigh line wing and depolarized combinational scattering line widths in critical mixtures

It has been experimentally found that at approaching the critical temperature of the exfoliating mixture carbon-disulfide-ethanol the widths of the Rayleigh line wing and the depolarized combinational scattering line drastically decrease. The same phenomenon was observed for 3 nitrobenzene combinational line scattering in a nitrobenzene—n-hexane mixture.     

Reorientational dynamics in a liquid organized system: Brillouin and depolarized Rayleigh scattering experiments in 1-octanol

Light scattering experiments, with dispersive and interferometric techniques, have been performed to study the orientational relaxation dynamics in 1-octanol, a structured liquid system having quite long living H-bonded clusters. Different temporal windows have been opened with these experiments to investigate the temporal events connected to the orientational relaxation dynamics of this molecular liquid. The present results have been compared with previous Monte Carlo MD simulations and experimental dielectric relaxation functions. They show that in the high frequency domain two additional very fast processes can be detected which have not been revealed by dielectric function relaxation.     

High intensity Rayleigh scattering by atoms

We investigate the elastic scattering of coherent high intensity radiation of X-ray frequency by aK-shell electron.     

Temperature measurements by coherent Rayleigh scattering

We demonstrate, for the first time to our knowledge, the utility of coherent Rayleigh scattering (CRS) for temperature measurements in low-density gases and weakly ionized plasmas by measuring the translational temperature of neutral argon in a glow discharge. By analysis of the near-Gaussian spectral profile of the CRS signal, we determine temperatures with an uncertainty of 相似文献   

First-order hyperpolarizability of ZnS nanocrystal quantum dots studied by hyper-Rayleigh scattering

Hyper-Rayleigh scattering technique was used to measure for the first time the first-order hyperpolarizability (β) of ZnS nanocrystals with 2.5 nm mean diameter. Results show that the ‘per ZnS particle’ β value is 2.34×10⁻²⁷ esu and the ‘per ZnS formula unit’ β value is 1.63×10⁻²⁸ esu. An increase by at least two orders of magnitude in the β value per ZnS formula unit is found when compared with bulk ZnS. Two possible contributions originating from nanocrystal surface electric field and solvent field were experimentally excluded. Other two contributions, bulk-like contribution and surface contribution, are considered. Especially, the latter is emphasized due to the special surface structure of nanocrystals.     

Anomalous density dependence in depolarized light scattering by simple fluids

An abrupt and possibly discontinuous change in the depolarized light scattering spectrum of fluid xenon with increasing density is reported. An approximate location of this anomaly in the phase diagram is given. The significance of the experimental observation in connection with equilibrium properties of the fluid is discussed.     

Determination of the thermal diffusion ratio in a binary mixture by forced Rayleigh scattering

After recalling briefly the results of the analysis of a forced Rayleigh experiment in a binary fluid mixture, one shows data obtained in a carbon disulfide-ethanol mixture. Estimating the derivatives of the susceptibility of the mixture from the Lorentz-Lorenz formula, one obtains values for the thermal diffusion ratio for several concentrations.     

Rayleigh scattering by sodium vapour in flames

In this paper we report on Rayleigh scattering measurements of sodium on the Na D-doublet in several premixed, laminar, shielded H₂/O₂/N₂, H₂/O₂/Ar and C₂H₂/O₂/N₂ flames at one atm. We performed the measurements under non-saturation conditions. The tunable CW dye-laser used produced linearly polarized light. The laser frequency was tuned well outside the absorption-line width of the sodium D-doublet lines. We have compared the ratio of Rayleigh scattering to collison-induced resonance-fluorescence (measured at fixed detunings of the laser) with theoretical predictions. In some flames, we also measured Rayleigh scattering and its polarization, as a function of detuning of the laser in the 4–40 Å region, for the red Na-D₁ and the blue Na-D₂ wings and found good agreement with theoretical predictions. Polarization of collision-induced fluorescence did not exceed 4% in this wavelength range.     

Study of polymerizing styrene through depolarized light scattering

The thermal polymerization of clean styrene has been studied through Rayleigh-Brillouin light scattering. The frequency shifts, Rayleigh to Brillouin intensity ratios, Rayleigh depolarization ratios, and depolarized intensities were measured as the polymerization proceeded to completion at 90°C. The depolarized intensities decreased and the frequency shifts increased smoothly from the monomer to the polymer values. The Vv intensities and Rayleigh to Brillouin intensity ratios increase dramatically during the first stages of polymerization then decrease systematically to their final values. There is a large increase in the Rayleigh to Brillouin intensity ratio from the monomer to the final polymer value. The vertical depolarization ratio pv and the horizontal depolarization ratio pV were found to be respectively 0.4 and 1 for the polymer. Our observations are explained in terms of light being scattered from concentration fluctuations in the early stages of polymerization and from spherically symmetric strain fields in the polymer. We believe that the background, which we observed to embrace a wide range of frequencies, was due to rotational Raman transitions.     

Experimental observation of universality in depolarized light scattering

Experimental results on light depolarization due to multimode scattering are reported. By means of polarization tomography, we characterize the depolarizing power and the polarization entropy of a broad class of optically scattering media and confirm the recently predicted universal behavior of these two quantities [Phys. Rev. Lett. 94, 090406 (2005)].     

Phase conjugate wavefront generation by forced Rayleigh scattering

Phase conjugate wavefront generation with efficiency up to 4% at 355 nm has been demonstrated in liquid media containing nonsaturating absorbers. Experimental results are qualitatively consistent with a simple theory of transient forced Rayleigh scattering which predicts the efficiency to depend upon the solvent, the square of the pump intensity and upon the beam quality but not upon the absorbing species.     

Paramagnetic magnetochiral effect in the H h and V h components of Rayleigh light scattering by molecular systems

A static magnetic field, acting on an isotropic medium composed of paramagnetic chiral molecules perpendicular to the propagation direction of the optical beam, is shown to induce an axial differential effect—magnetochiral Rayleigh light scattering. Diamagnetic and paramagnetic contributions to the effect are given in terms of the linear and nonlinear electric dipole, magnetic dipole and electric quadrupole polarizabilities responsible also for natural optical activity, the Faraday effect as well as magnetochiral birefringence. Specific cases are discussed.