The spectrum of depolarized light scattered from critical mixtures

The temperature dependence of the spectrum of depolarized light scattering in a uniform phase of critical mixtures of n-dodecane-ββ' dichlorodiethyl ether and n-hexane-nitrobenzene is studied experimentally. The depolarized light scattering spectrum was found to narrow dozens of times in the temperature interval from 30 to 1°C from the critical temperature of exfoliation in both mixtures. The results obtained are discussed.     

The spectrum of depolarized light scattered from a critical nitrobenzene-n-hexane mixture

Both linewidth and intensity measurements have been performed on the depolarized reorientation spectrum of a critical mixture of nitrobenzene-n-hexane. No critical behaviour of the linewidth or intensity was observed. The measurements are in very good agreement with all extrapolated data or expected values for binary nitrobenzene mixtures far from their critical point.     

Spectrum of depolarized light scattered from nitroethane-isooctane mixture near its critical point

We present the results of a study of the spectrum of depolarized light scattered from the critical nitroethane—isooctane mixture which has a very weak critical opalescence. Near the critical point only slight narrowing of the spectrum is observed.     

Fluctuation characteristics of singly scattered light intensity

The correlation function and variance of the intensity fluctuations of singly scattered light are computed for a system of independent scatterers subjected to Brownian motion and illuminated by a light beam. The computation is carried out taking account of space and time averaging by the detector. The results obtained agree with available test data.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 120–124, May, 1973.     

Effects of light quenching on the emission spectra and intensity decays of fluorophore mixtures

We examined a series of fluorophore mixtures to determine the wavelength selectivity of light quenching and the effects of light quenching on the emission spectra and intensity decays. Light quenching can be accomplished using a single excitation pulse train and quenching wavelength (one-beam) or with longer-wavelength quenching pulses time-delayed relative to the excitation pulses (two-beam). Both one-beam and two-beam light quenching were found to alter the intensity decays of the mixtures. The frequency-domain intensity decay data were analyzed to reveal the fractional intensity of each fluorophore in the mixture and the effects of light quenching on the fractional contribution of each fluorophore to the total intensity. Fluorophores were selected to provide a range of decay times and emission wavelengths. The extent of quenching in the mixtures was dependent on which fluorophore had the higher radiative decay rate and emission intensity at the quenching wavelength. A general theory is presented which describes the intensity decays in terms of the extent of quenching of each fluorophore and the time delay between excitation and quenching pulses. The effects of light quenching on the fractional intensities of each fluorophore in the mixture, recovered from the intensity decay analysis, were found to be in quantitative agreement with that predicted from steady-state measurements of light quenching and from the spectral properties of the fluorophores. The data on light quenching of mixtures demonstrate that light quenching may be used for selective quenching of fluorophores and thus of potential value for studies of multichromophoric systems.     

Spectral measurements of the depolarized multiple scattered light from a binary mixture near its critical point

We report the first spectral measurements of the depolarized multiple scattered light from a binary mixture near its critical point. Spectral analysis of the depolarized light allows to separate rigorously the multiple scattering from the light scattered by the anisotropy fluctuations. The results are in very good agreement with a recent theory by Oxtoby-Gelbart.     

Spectrum and intensity of light scattered from SF6 along the coexistence curve

Our two groups have measured independently the “Rayleigh linewidth” (Γ), the reduced compressibility (??/?μ)_T, and the pressure (P) of SF₆ along the liquid and vapor sides of the coexistence curve. We find that (??/?μ)_T = 1.67 × 10^-10 (1 - T/T_c)^{-1.22 ± 0.015}g²erg^-1cm^-3 and (?P/?T)lχ = (7094 ± 0.1) × 10⁵ dyne/cm² ° We analyze our linewidth measurements in terms of the Kadanoff-Swift-Kawasaki mode-mode coupling theory using estimates for the viscosity and correlation range.     

Correlation between intensity fluctuations of light scattered from a quasi-homogeneous random media

The correlation between intensity fluctuations of light scattered from a quasi-homogeneous random media was analytically derived. We showed the correlation depends on spatial Fourier transforms of both the intensity and degree of spatial correlation of scattering potentials of the media, while the normalized correlation equals the squared modulus of the degree of spatial coherence of the scattered fields.     

Coherence and polarization properties in speckle of totally depolarized light scattered by totally depolarizing media

When a totally unpolarized light is scattered by a medium that spatially totally depolarizes incident polarized light, the scattered field presents an increase of the order described by the temporal degree of polarization. We analyze the behavior of some polarization and coherence properties in such a physical situation.     

Investigation of the spectra of depolarized light scattering in two viscous liquids

The fine structure of the Rayleigh line wing was studied experimentally in a broad temperature range in the viscous guaiacol liquid. The propagation velocity and the absorption coefficient of the transverse hypersound were determined by the Rayleigh line wing spectra at temperatures from ?27 to ?85°C. The transverse hypersound absorption is shown to pass through its maximum at a temperature of ?34°C. The experimental data for two vitrifying viscous liquids, namely, guaiacol and salol were analyzed. The limiting elastic bulk moduli were found to intersect at the crystallization temperature and the limiting shear modulus to vanish at this temperature. These and other specific features of the guaiacol and salol behavior at the crystallization temperature, revealed in this and previous our studies, point to the possibility of the existence of two phases in a liquid.     

激光等离子体受激Raman散射光谱的时间分辨测量

采用光学多道谱仪和光学条纹相机耦合,组成时间分辨的Raman散射光谱测量系统,可实现0.5nm的光谱分辨和好于10ps的时间分辨。采用该测量系统,在神光Ⅱ装置上开展了脉宽1ns、波长351nm的激光与两种不同尺寸柱腔靶相互作用的物理实验,获得了时间分辨的SRS光谱实验结果。研究表明,SRS光谱在时间上相对于入射激光有一定的延迟,腔靶尺寸减小时,延迟时间随之减小。通过长、短波截止波长分析电子密度方法,计算得出了Ⅰ型和Ⅱ型腔靶SRS散射光最短波长光谱发生的密度区分别为0.069nc和0.027nc。     

激光等离子体受激Raman散射光谱的时间分辨测量

采用光学多道谱仪和光学条纹相机耦合,组成时间分辨的Raman散射光谱测量系统,可实现0.5 nm的光谱分辨和好于10 ps的时间分辨。采用该测量系统,在神光Ⅱ装置上开展了脉宽1 ns、波长351 nm的激光与两种不同尺寸柱腔靶相互作用的物理实验,获得了时间分辨的SRS光谱实验结果。研究表明,SRS光谱在时间上相对于入射激光有一定的延迟,腔靶尺寸减小时,延迟时间随之减小。通过长、短波截止波长分析电子密度方法,计算得出了Ⅰ型和Ⅱ型腔靶SRS散射光最短波长光谱发生的密度区分别为0.069nc和0.027nc。     

The depolarization of light scattered from rough metal surfaces

To describe the depolarization of the electromagnetic field scattered from rough metal surfaces, a finite, non-vanishing value of the conductivity has to be considered. To reveal the modifications imposed by a complex dielectric constant, the Beckmann formula is expanded in power series of slope terms. We then arrive at an analytic expression which is convenient for evaluation as a function of the parameters involved. With this expression, plots of the cross-polarization ratio vs. angle of incidence and vs. slope are presented.     

Angular intensity distribution of scattered light in systems of closely spaced particles

The results of experimental and computational investigations of the dependence of the angular intensity distribution of scattered light on the concentration of scatterers are discussed. It is shown that a high density of small and large scatterers in a three-dimensional system results in a deformation of the scattering indicatrix. The changes in the angular distribution of intensity of the scattered light at large concentrations are explained by the appearance of fields of multiply scattered waves at significantly lower optical thicknesses than for independent scatterers.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 99–103, March, 1976.     

Pressure and temperature variation of the depolarized light scattering spectra of the fragile glass-former liquid salol

The pressure and temperature dependences of the depolarized light scattering spectra of salol have been measured at isobaric condition P = 1 bar for T between 328 and 393 K, and at isothermal condition T = 343 K for P between 1 and 625 bar, i.e. outside the metastable liquid region. The experimental results for both the α- and β-relaxations can be well described by the Mode Coupling Theory. The independence of the power-law parameters a, and consequently b and γ, from the thermodynamic variables T and P is demonstrated.The critical temperature T _c at 1 bar and the critical pressure P _c at T = 343 K have been determined from the normal liquid state. Received 2 May 2000     

Particulate concentration measured from scattered light fluctuations

Scintillation of scattered radiation caused by particulate matter is studied. By use of stochastic theory, expressions for mathematical expectation, variance, and scintillation index are derived. A method of measuring particulate-mass concentration with the scintillation index is proposed. The major advantage of this method is its insensitivity to lens contamination and particle-color change.     

平面反射镜表面散射光干涉

激光束照射到表面被粘污的反射镜上会产生干涉环,入射光束和反射光束在被粘污表面产生散射光干涉.随着入射角的变化,光束在反射镜玻璃片内光程改变,引起干涉环从中心冒出或缩进,干涉环级数的变化与入射角的平方成正比.