On the entropy-fluctuation contribution to Rayleigh scattering of light

We discuss the power spectrum due to entropy fluctuations near the surface for quasielastic Rayleigh scattering in isotropic crystals. A back-scattering, oblique incidence geometry, is used in our theoretical calculations. Some interesting novel aspects are presented and their importance is discussed.     

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.     

Rayleigh scattering of nanosecond light pulses

The relation _t/_theory = (₁/)[–exp(–t/)], obtained by M. Skowronek and J. Alayli for Rayleigh scattering of light pulses, is experimentally investigated. Relative measurements of scattering are made in Ar and N₂ without taking into account instrumental effects. It is shown that the level of scattering in a gas medium is independent of the pulse duration t for a pulse with a wavelength of = 0.53 m in the range 2 ns t 30 ns.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 49–54, October, 1985.     

Investigation of the Soret effect in binary liquid mixtures by thermal-diffusion-forced Rayleigh scattering (contribution to the benchmark test)

Within the framework of an international benchmark test we have performed measurements of the transport coefficients S T (Soret coefficient), D (mutual diffusion coefficient) and D T (thermal diffusion coefficient) on the three binary organic liquid mixtures 1,2,3,4-tetrahydronaphthalene- n -dodecane, 1,2,3,4-tetra- hydronaphthalene-isobutylbenzene and isobutylbenzene- n -dodecane with the weight fraction c = 0.5 at T = 298.15 K by means of thermal-diffusion-forced Rayleigh scattering (TDFRS) for benchmarking purposes. Our results for the coefficients are in good agreement with those obtained by annular and parallelepipedic thermogravitational columns and by other benchmark tests which also apply TDFRS measurements.     

Four-wave mixing Rayleigh scattering spectroscopy of binary solutions

The concentration dynamics of the scattering spectral width in a number of binary solutions has been studied by four-wave mixing spectroscopy near the Rayleigh resonance. It is noted that, according to the classical concepts, a variation in the correlation length of fluctuations of the relative concentration of molecules in a solution plays a key role in the change in the spectral width. Some liquids exhibit nonmonotonic (hysteretic) concentration dependences of the Rayleigh linewidth.     

Comments on “the Rayleigh line wing and the coefficient of depolarization of scattered light in critical mixtures”

Independent measurements of the linewidth of the depolarized Rayleigh line in the critical mixture of nitrobenzene and n-hexane, persistently disagree with each other. We thus analyse here the limitations of the experimental methods and show that the strong critical narrowing observed by Fabelinskii et al. is probably an experimental artefact.     

Rayleigh scattering of light by two-dimensional electrons in a high magnetic field

Resonance Rayleigh scattering of light by a two-dimensional electron system in the ultraquantum limit is investigated. The scattering process under study involves electronic states belonging to the two spin sublevels of the zero Landau level. It is shown that the main contribution to resonance Rayleigh scattering originates from the fluctuations of the random potential in the quantum well hosting the two-dimensional system.     

Superradiant Rayleigh scattering of light by the Bose-Einstein condensate of rarefied atomic gases

The superradiant Rayleigh scattering of high-intensity light pulses by the Bose-Einstein condensate of rubidium vapor is studied using the model proposed earlier. It is demonstrated that four states with a certain momentum are occupied under the experimental conditions (two states correspond to the forward recoil and two others correspond to the backward recoil). Condensate pulsations between the zero-momentum state and the above states are detected and studied. The corresponding shape of the coherent Rayleigh pulse is found.     

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.     

Rayleigh light scattering in molecular crystals of succinonitrile and trimethylacetonitrile

Two representatives of molecular crystals exhibiting plastic phase : succinonitrile NCCH₂CH₂CN and trimethylacetonitrile |CH₃|₃CCN were studied. For these crystals the horizontally and vertically polarized components of the scattered radiation were measured in the temperature range from the plastic phase to liquid, and the depolarization degrees were determined. The isotropic component V_V was also measured as a function of temperature changing from liquid to plastic phase. In both phases the squares of effective anisotropy of optical polarizability were found from the measurements of the anisotropic component H_V.     

Optical-acoustic soliton under the conditions of slow light and stimulated Mandelstam-Brillouin scattering

The possibility of forming a stable optical-acoustic soliton in the regime of electromagnetically induced transparency has been analyzed under the condition that the group velocity of light in a medium with stimulated Mandelstam-Brillouin scattering decreases to the speed of sound. This possibility exists because the forward Mandelstam-Brillouin scattering, which is forbidden in a nondispersive medium, is allowed under this condition. The optical component is an envelope pulse, and the acoustic component has no carrier frequency. It has been shown that such a soliton can be formed for anomalously low input intensities of the optical pulse.     

Superradiant resonant Rayleigh scattering of light by the Bose-Einstein condensate of rarified atomic gases

Based on the earlier model, the superradiant Rayleigh scattering of the high-intensity short light pulses by the Bose-Einstein condensate of rubidium vapor is studied. It is demonstrated that only six states with a certain momentum are filled when the resonance detuning is about the Rabi frequency. The first two states describe the atomic motion along the condensate due to absorption, whereas the remaining four states describe the atomic motions at angles of 45° and 135° to the condensate axis owing to the reemission of the photon. The condensate pulsations between the state with zero momentum and the last four states are revealed. The corresponding shape of the coherent Rayleigh pulse is found for various resonance detunings.     

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.     

Rayleigh light scattering in molecular crystals of pivalic acid and nitro-t-butane

Two representatives of molecular crystals exhibiting plastic phase: pivalic acid (CH₃)₃CCOOH and nitro-t-butane (CH₃)₃CNO₂ were studied. For these crystals the polarized and depolarized components of the scattered light were measured in the temperature range from the plastic to liquid phase and the depolarization degrees were determined. In both phases the square of effective anisotropy of optical polarizability Γ² and the parameter of angular correlations J_A were found from the measurements of the depolarized component R_vh.     

Rayleigh scattering induced by static bends of layers in a smectic A liquid crystal

We observe the anisotropy and the polarization properties of the Rayleigh scattered light for a planar smectic A texture of butoxyl benziledene-p-n anilino-acetophenone (BBAA). This scattering is attributed to static bends of the smectic layers, with wave vectors parallel to the smectic planes. This effect gives a simple method to measure the ratio of the extraordinary to the ordinary indices: n_e/n₀ = 1.18 at 89°C.     

Ionic reorientational motions in aqueous solutions: a depolarized light scattering study of NO3 - and SCN-

Depolarized Rayleigh scattering has been measured in the frequency range 0·2 cm^-1 to 200 cm^-1 using a triple monochromator and Fabry-Perot interferometry for solutions of ammonium, sodium and lithium nitrates, for nitric acid and ammonium and potassium thiocyanate over a range of concentrations and temperatures. From comparisons with scattering from water and alkali halide solutions it is concluded that the narrow central component of the scattering arises predominantly from anion reorientational motions. From intensity measurements there is no evidence for significant anion-anion correlations. Infinite dilution relaxation times are discussed in relation to the motions of water molecules in the hydration spheres. Except for very dilute solutions, a simple hydrodynamic model accounts for the temperature and concentration dependence of SCN^- reorientation. For NO₃ ^- it is necessary to assume that the boundary conditions are concentration dependent. In very concentrated nitrate solutions the lineshape is non-lorentzian due, it is argued, to specific cation-anion interactions.