Showing papers on "Light scattering published in 1969"
TL;DR: In this article, the power spectrum of the light scattered by a two-level atom driven near resonance by a monochromatic classical electric field is evaluated, where the atom is assumed to relax to equilibrium with the driving field via radiation damping, which is treated by explicitly coupling the atom to quantized electromagnetic field modes.
Abstract: The power spectrum of the light scattered by a two-level atom driven near resonance by a monochromatic classical electric field is evaluated. The atom is assumed to relax to equilibrium with the driving field via radiation damping, which is treated by explicitly coupling the atom to the quantized electromagnetic field modes. The power spectrum of the scattered field is directly obtainable from the two-time atomic dipole moment correlation function, which is evaluated by a method based on a Markoff-type assumption analogous to that used to evaluate the time evolution of single-time atomic expectation values.
1,357 citations
TL;DR: In this article, the spectral absorption coefficient and the total emissivities of soot suspensions were calculated for the room temperature optiaI.1 and 2.5-1O.
Abstract: Data on the room temperature optiaI.1 constants of soot are presentedfor the 'Wavelength regions 0.4-().8j.1 and 2.5-1O.0j.l. Dispersion formulas are developedfor interpolating the data between0.8 and 2.5j.1. The results are used to calculate the spectral absorption coefficient and the total emissivities of soot suspensions. It is shown that the correct values of the optiaI.l constants are neededin the use of light-scattering techniques for the measurement of the soot concentration but that uncertainties introduced in flux
746 citations
TL;DR: In this paper, the theory of light scattering from a collection of free electrons is reviewed, and it is shown that the frequency spectrum observed at a detector is precisely that of the density fluctuations of a particular scale length in the scattering medium, the scale length being determined by the wavelength of the incident light and the geometry of the experimental arrangement.
Abstract: The theory of light scattering from a collection of free electrons is reviewed, and it is shown that the frequency spectrum observed at a detector is precisely that of the density fluctuations of a particular scale length in the scattering medium, the scale length being determined by the wavelength of the incident light and the geometry of the experimental arrangement. The electron density fluctuation in a plasma is calculated, and it is shown that the plasma Debye shielding distance λD is a critical length in the theory, the electrons behaving independently on a scale shorter than λD and collectively on a scale longer than λD. The collective behaviour is characterized by the presence of waves that can give rise to well-defined resonances in the scattered-light spectrum. The effects of differing ion and electron temperatures, current flowing in the plasma, magnetic field, and Coulomb collisions are considered briefly. Technical considerations in planning experiments to test the theory and to apply it to the diagnosis of real laboratory plasmas are discussed, with attention being given to signal-to-noise ratio, stray light, and the dispersing instrument to be used at the detector. Some representative experiments that have been carried out are reviewed.
381 citations
TL;DR: Comparison of theoretical results and experimental values for transmittance through rabbit cornea shows that the quasi-regular quasi-random structure revealed by the electron microscope is not in conflict with transparency.
Abstract: The physical basis for the transparency of the cornea to visible light is investigated theoretically in terms of the molecular structure as depicted by electron microscopy. Electron micrographs show that the major portion of the cornea contains long cylindrical fibrils arranged in a quasi-random fashion, with local order extending over distances comparable to the wavelength of light. Heretofore, the generally accepted explanation of transparency has been in terms of a supposed crystalline arrangement of the fibrils, because this was the only distribution that could ensure transparency on a simple theoretical basis. Thus, the non-crystalline structure shown by the electron microscope has been widely regarded as an artifact due to the fixation procedure. In the present work, the light scattering from the fibrils is formulated in terms of their radial distribution function, which is determined by numerical analysis of electron micrographs. Comparison of theoretical results and experimental values for transmittance through rabbit cornea shows that the quasi-regular quasi-random structure revealed by the electron microscope is not in conflict with transparency.
254 citations
01 Apr 1969
TL;DR: In this article, a simple phase screen technique was used to derive statistical characterizations of the perturbations imposed upon a wave (plane, spherical, or beamed) propagating through a random medium, including time-lagged functions, mixed functions involving phase and amplitude fluctuations, angle-of-arrival covariances, frequency covariance, and other higher order quantities.
Abstract: A simple phase-screen technique has been used to derive statistical characterizations of the perturbations imposed upon a wave (plane, spherical, or beamed) propagating through a random medium. The method is essentially physical rather than mathematical; its application is limited only by the weak-scattering approximation, a limitation which is important only for long optical or acoustical paths. No other wavelength restriction is imposed. Situations treated include arbitrary path geometries, finite transmitting and receiving apertures, anisotropic or lossy media, and polarization effects. Results include, in addition to the usual statistical quantities, time-lagged functions, mixed functions involving phase and amplitude fluctuations, angle-of-arrival covariances, frequency covariance, and other higher order quantities.
199 citations
TL;DR: Volume distributions of mammalian cells and plastic microspheres agree with other independent determinations on small angle light scattering by spherical particles.
Abstract: Theory predicts that small angle light scattering by spherical particles of 5 to 20 μ diam is nearly proportional to volume and insensitive to particle refractive index. A flow system photometer with helium‐neon laser light source measures the scattering between 0.5 and 2.0° from individual particles at 104 to 105/min. Volume distributions of mammalian cells and plastic microspheres agree with other independent determinations.
198 citations
TL;DR: In this paper, the spectrum of light scattered by a suspension of particles in a fluid was used to obtain quantitative information about the motion of the particles, including an accurate determination of their diffusion constant.
Abstract: From the spectrum of light scattered by a suspension of particles in a fluid one can obtain quantitative information about the motion of the particles, including an accurate determination of their diffusion constant. If the incident light source is a laser, and the scattered light falls on the photosurface of a photomultiplier tube, then by measuring the spectrum of the photocurrent one obtains the spectrum of the intensity fluctuations of the scattered light. The intensity of the scattered light is determined by the instantaneous superposition of the phases of the waves scattered from each of the diffusing particles and the intensity fluctuates because the particles move. For particles of known diameter one can predict the spectral shape and width from the diffusion equation. We present a calculation of the spectrum of the field and the spectrum of the intensity of the scattered light and an advanced laboratory experiment and lecture demonstration by which the intensity spectrum can be studied.
161 citations
TL;DR: In this paper, the problem of multiple scattering by a plane parallel atmosphere with anisotropic phase functions typical of cloud and haze particles was studied and the resulting albedos, angular distributions of intensities, and planetary magnitudes were compared to solutions obtained with approximate analytic phase functions and, in the case of the cloud phase function, to the solution obtained with the forward diffraction peak omitted from the phase function.
Abstract: Solutions are obtained for the problem of multiple scattering by a plane parallel atmosphere with anisotropic phase functions typical of cloud and haze particles. The resulting albedos, angular distributions of intensities, and planetary magnitudes are compared to solutions obtained with approximate analytic phase functions and, in the case of the cloud phase function, to the solution obtained with the forward diffraction peak omitted from the phase function. It is shown that the cloud phase function with the truncated peak yields results practically identical to those obtained with the complete cloud phase function, not only for albedos and magnitudes, but also for the angular distribution; the approximation introduces errors of several per cent in the angular distribution for direct backscattering (the region of the glory), for emergent angles near grazing regardless of the incident angle, and, of course, a larger error occurs for total scattering angles near 0°. However, the errors are unimpor...
150 citations
TL;DR: The spectrum of the light scattered by a binary solution is calculated from thermodynamic fluctuation theory and the linearized hydrodynamic equations appropriate to a two-component fluid as discussed by the authors, where the spectrum consists of three peaks.
Abstract: The spectrum of the light scattered by a binary solution is calculated from thermodynamic fluctuation theory and the linearized hydrodynamic equations appropriate to a two‐component fluid The spectrum consists of three peaks Expressions are obtained for the positions and widths of the two‐side, Brillouin peaks In general the central, unshifted Rayleigh peak is found to consist of a superposition of two Lorentzians that involve the combined dynamical effects of heat conduction and diffusion The condition is stated under which it is possible to separate the central peak simply into two contributions, one arising from diffusion and one from thermal conduction For many binary systems this separation is justified In these cases measurement of the spectrum of the scattered light should prove to be an attractive alternative means of measuring the diffusion coefficient of binary solutions
143 citations
TL;DR: It is shown how a single hologram method of analysis, utilizing parallax and fringe counting, and a multiple holographic interferometry method, using interference order assignment are related.
Abstract: A general relation is derived by which small displacements of a diffusely reflecting surface may be determined using holographic interferometry. It is shown how a single hologram method of analysis, utilizing parallax and fringe counting, and a multiple hologram method, using interference order assignment are related. Both methods may be viewed in a unified manner. The requirements for application of both methods are discussed.
129 citations
01 May 1969
TL;DR: In this article, the effect of light scattering properties on the orientation of the ceramic polar axis (electrical poling direction) has been investigated and shown to be independent of the magnitude of electrical poling (ferroelectric remanence state).
Abstract: Thin polished plates of hot-pressed rhombohedral lead zirconate-lead titanate ceramics possess one of two types of electro-optic properties depending on the nominal grain diameter. In poled coarse-grained ceramics the electrooptic effect of importance for devices is the dependence of the light scattering properties on the orientation of the ceramic polar axis (electrical poling direction). The light scattering properties are essentially independent of the magnitude of electrical poling (ferroelectric remanence state). Poled fine-grained ceramics are birefringent, and their light transmission characteristics are similar to those of optically uniaxial crystals. These materials exhibit orthotropic symmetry with respect to the optic axis, which coincides with the ceramic polar axis. The fine-grained ceramic electrooptic effect of primary importance for devices is the dependence of the effective birefringence on the magnitude of electrical poling as well as on the intensity of the applied biasing electric field. Retardation of a ceramic plate can be varied incrementally by partial switching or continuously by application of a nonswitching bias field. Both coarse- and fine-grained ceramics have the property that localized areas as small as 25 µ by 25 µ can be poled or switched independently without affecting the light transmission characteristics of the surrounding area. The locally switched areas are stable with time, but they can be "erased" by switching them back to their original orientation. Each locally switched area can function as a light shutter, valve, or spectral filter depending on the ceramic material, the switching mode, and the characteristics of the incident light.
TL;DR: In this article, light scattering experiments on semiconductors are discussed in which the energy of the incident photon from the laser or that of the Raman-scattered photon is nearly coincident with that of an electronic transition in the scatterer.
Abstract: Light scattering experiments on semiconductors are discussed in which the energy of the incident photon from the laser or that of the Raman-scattered photon is nearly coincident with that of an electronic transition in the scatterer. Experimental data on ZnTe, CdS, InAs, ZnSe, and GaP are analyzed, and a discussion of LO-overtone scattering mechanisms is presented. Some additional experiments are proposed and discussed.
TL;DR: In this paper, the authors show that the inelastic scattering of light arising from the time-dependent polarizability induced by intermolecular interactions has been observed in the simple classical liquid, argon.
Abstract: The inelastic scattering of light arising from the time-dependent polarizability induced by intermolecular interactions has been observed in the simple classical liquid, argon. The spectrum at 90 \ifmmode^\circ\else\textdegree\fi{}K and 1.5 atm is centered at zero frequency shift, and is exponential in shape, with a characteristic width of 21 ${\mathrm{cm}}^{\ensuremath{-}1}$. The depolarization ratio for the scattered light is 0.72 \ifmmode\pm\else\textpm\fi{} 0.02, implying that the anisotropy of the polarizability dominates the scattering. The liquid spectra are compared with previously obtained spectra in gaseous argon and with the low-temperature gas data obtained in the present work. Both the linewidth and intensity for the liquid spectra suggest the inadequacy of the simple collision-induced view of the scattering process when clustering occurs. Calculations of the liquid spectrum, based on a model which is a generalization of the second-order Raman effect, yield for the liquid the correct line shape and a linewidth much closer to that observed than does the binary collision model. The lack of structure in the spectrum is taken as direct evidence against the existence of well-defined collective modes of short wavelength in liquid argon.
TL;DR: Hardened gelatin films sensitized with ammonium dichromate can be utilized to record high quality holograms and the maximum diffraction efficiency of the hologram approaches 90%.
Abstract: Hardened gelatin films sensitized with ammonium dichromate can be utilized to record high quality holograms. The maximum diffraction efficiency of the hologram approaches 90%. The light scattering from the hologram is so low that under ordinary light the hologram plate appears almost indistinguishable from a clear glass plate. Either a transmission or a reflection hologram can be recorded. Linear recording range of light amplitude is large. A practical method of preparing and processing the film is described, and the exposure characteristics are presented.
TL;DR: In this article, the effect of a distribution of orientation of the rods is explored, leading to a change in scattering patterns produced by orienting the rods upon stretching the sample, and theoretical patterns are compared with experimental ones obtained upon stretching polytetrafluorethylene.
Abstract: : The scattering patterns are calculated from anisotropic rods having an arbitrary orientation of the principal polarizability axis with respect to the rod axis. The effect of a distribution of orientation of the rods is explored, leading to a change in scattering patterns produced by orienting the rods upon stretching the sample. Scattering patterns are affected by the relationship between the refractive indices of the rods and that of the surroundings. The influence of the optic axis orientation angle changing upon orienting the rods is explored. Theoretical patterns are compared with experimental ones obtained upon stretching polytetrafluorethylene (PTFE) films. (Author)
TL;DR: In this paper, the antisymmetric components Ckja = (Ckj − Cjk)/2 of the polarizability tensor were investigated for non-resonance-dipole light-scattering cross sections.
Abstract: Quantum-mechanical expressions for nonresonance-dipole light-scattering cross sections are related to corresponding expressions for oscillator strengths and refractive indices. In particular, Rayleigh and Raman cross sections for atoms are expressed in terms of oscillator strengths and vector-coupling coefficients. Several of our results, including the relationship between Rayleigh scattering and refractive index, differ in general from the corresponding results of classical dispersion theory. We show that these differences arise from antisymmetric components Ckja = (Ckj − Cjk)/2 of the polarizability tensor, which have been neglected in the classical analyses. Calculated Rayleigh cross sections for cesium and aluminum atoms, and Raman cross sections for aluminum atoms are presented to illustrate our results. The antisymmetric contribution is found to be substantial in all of these cross sections; its most obvious effect is to cause the depolarization (for linearly polarized incident light) to exceed 34 over extended wavelength ranges away from resonance. On the other hand, for atoms initially in states of zero angular momentum, and molecules under conditions which allow the use of Placzek’s polarizability approximation, our results agree with those of classical dispersion theory.
TL;DR: In this article, the volume scattering function is converted to an image modulation transfer function and the inverse transform is also derived so that the scattering properties can be calculated, given the loss of resolution.
Abstract: Multiple scattering of light by particles suspended in liquid can be a cause of degraded optical resolution. This is especially significant when the particles are relatively large and numerous, but most of the scattered power is deflected through very small angles, owing to a near match between the refractive indices of the particles and the medium. Formulas which convert the volume scattering function to an image modulation transfer function are derived for this case. This conversion allows calculation of image degradation, given the scattering properties of the medium. The inverse transform is also derived so that the scattering properties can be calculated, given the loss of resolution. The latter is best measured by imaging a set of paralled bar patterns having a wide range of spatial frequencies. The conversion from scattering function to optical transfer function is interpreted in general and evaluated for one published scattering function measured in sea water. The results are compared to published image measurements in fresh water.
TL;DR: In this article, the size distributions and particle concentrations were obtained in situ using light scattering techniques, and the particle sizes and particle densities were obtained by using a light scattering technique on the chromium hydroxide sol sol of submicronic particles.
TL;DR: In this paper, a generalization of the Kirkwood g factor to second-rank tensors is defined for light scattering by liquids of anisotropic molecues, in a more compact form.
Abstract: Tensor‐algebra techniques are used to derive expressions similar to those of Pecora and Steele for light scattering by liquids of anisotropic molecues, in a more compact form. The correlation functions are cast into a form in which their geometrical meaning is made obvious and is more immediately applicable to liquid models. A generalization of the Kirkwood g factor to second‐rank tensors is defined. The theory is applied to the depolarized Rayleigh wings. It is argued on the basis of intensity and half‐width measurements that the diffuse line, which appears in the spectrum of benzene and several benzene derivatives, originates from reorientation of single molecules. This conclusion fits into a broader scheme incorporating results of dielectric, NMR, and viscosity measurements. It is suggested to relate the background, together with the narrow hole in the middle of the depolarized spectrum, to couplings of orientational fluctuations with shear waves.
TL;DR: There are subtle structural and biochemical differences between bacterial species, and average differences should be expected in their dielectric composition, so the light scattering characteristics of one species might well differ from those of another species.
Abstract: I HAVE already discussed the feasibility of identifying living bacterial cells using differential light scattering techniques1. I suggested that, because there are subtle structural and biochemical differences between bacterial species, average differences should be expected in their dielectric composition. Thus the light scattering characteristics of one species might well differ from those of another species. Light scattering characteristics could therefore serve as a means of identification. Naturally, variations in size and shape, growth history and environmental effects on cellular morphology would be expected to modify light scattering differences and perhaps render such an identification procedure meaningless.
IBM1
TL;DR: The intensity and the degree of polarization of the radiation scattered by a large sphere were computed using the Mie theory at sufficiently small interval of the scattering angle for obtaining a complete picture of all the characteristics of the field of the scattered radiation.
Abstract: The intensity and the degree of polarization of the radiation scattered by a large sphere were computed using the Mie theory at sufficiently small interval of the scattering angle for obtaining a complete picture of all the characteristics of the field of the scattered radiation. The results are presented for four different sizes of the water sphere (radius = 6.25 micro, 12.5 ;micro, 25.0 micro, and 50.0 micro) assumed to be illuminated by an unpolarized beam of monochromatic radiation with wavelength 0.4 micro. A detailed comparison is then made between the results obtained using the exact Mie theory and those obtained using an approximate approach based on the application of the other laws of the geometrical and physical optics. The angular positions of the primary and secondary rainbows, as well as those of their supernumerary bows as obtained using the approximate method, agree with those obtained from the Mie theory only if the size parameter of the sphere is of the order of 800. Besides the phenomenon of glory which is not amenable to explanation in terms of the geometrical and physical optics, the Mie computations bring out several distinct maxima and minima whose occurrence cannot be explained in likewise manner.
TL;DR: In this paper, a theoretical analysis of acoustooptical pulse modulators is carried out that yield the intensity and rise time of the scattered light and the optimum relationship between the dimensions of the optical and acoustic beam is given.
Abstract: A theoretical analysis of acoustooptical pulse modulators is given Calculations are carried out that yield the intensity and rise time of the scattered light The optimum relationship between the dimensions of the optical and acoustic beam is given A fast high-efficiency modulator has been built based on the theoretical results The modulator is composed of a 350-MHz ZnO transducer sputtered on a quartz acoustic lens and an As 2 S 3 glass serving as the modulating material With 06 watt of electrical RF peak power driving the modulator, 70 percent of the light intensity (at 063μ) is deflected The rise time of the scattered light pulse is of the order of 6 ns
TL;DR: In this paper, the problem of resonant scattering of polaritons is solved for short-range exciton-impurity interactions in a natural fashion, and the giant oscillator strengths of bound-exciton transitions are also automatically obtained.
Abstract: To calculate correctly the scattering of light by phonons or impurities in a crystal, the true asymptotic scattering states of the coupled system of crystal plus light (polaritons) should be used. When the light frequency is close to one exciton or optical-phonon frequency, the polariton is entirely excitonlike, and the polariton scattering can, in the Born approximation, be related to exciton scattering properties. If the exciton itself interacts strongly with an imperfection in the crystal, it is not permissible to treat either the exciton scattering or the exciton-photon interaction as perturbations. This problem of resonant scattering of polaritons is solved for short-range exciton-impurity interactions. Radiative damping and spatial dispersion appear in this solution in a natural fashion. Giant oscillator strengths of bound-exciton transitions are likewise automatically obtained. The proper inclusion of radiative damping and spatial dispersion keeps all cross sections finite. The relation between the theory and experiments is briefly discussed.
TL;DR: It is shown that the red shift and decrease in amplitude of the CD extrema of particulate systems correlate with changes in the intensity of scattered light and with the extent of absorption flattening as measured, respectively, at wavelengths where significant absorption does not occur and at wavelengths corresponding to major absorption bands.
TL;DR: In this paper, the diffuse reflection and transmission of light by a plane-parallel suspension of randomly oriented particles, scattering independently, are treated using radiative-transfer theory and exact allowance is made for external and internal reflection at the plane surfaces of the matrix.
Abstract: The diffuse reflection and transmission of light by a plane-parallel suspension of randomly oriented particles, scattering independently, are treated using radiative-transfer theory. Exact allowance is made for external and internal reflection at the plane surfaces of the matrix. General equations are derived in a form suitable for automatic computation. Some comparisons made between theoretical predictions and experimental measurements of the total transmittance of an optically thick diffusing suspension show satisfactory agreement with radiative-transfer theory and also with the Eddington approximation.
TL;DR: In this paper, the authors verified Koschmieder's formula relating visibility to the extinction coefficient (L υ = 3.9/b ) by comparing simultaneous measurements of both variables at one site.
TL;DR: In this article, the resonant scattering of monochromatic light in gases is analyzed and explicit expressions for the differential cross section are obtained in the limits (Doppler width) \ensuremath{\gg} (natural width), (collision width), and (Collision width)
Abstract: The resonant scattering of monochromatic light in gases is analyzed. Explicit expressions for the differential cross section are obtained in the limits (Doppler width) \ensuremath{\gg} (natural width) \ensuremath{\gg} (collision width) and (collision width) \ensuremath{\gg} (natural width) \ensuremath{\gg} (Doppler width). In the former limit, the frequency distribution of scattered light is narrowed in the forward and backward directions, and has the full absorption width for right-angle scattering. In the collision-dominated limit, the cross section separates into a coherent and a fluorescent component. The motion of the atoms broadens the $\ensuremath{\delta}$ function distribution characterizing coherent scattering from a stationary target. The interference between light scattered by different atoms is assessed.
TL;DR: The dispersive color reflections in both the undisturbed and disturbed films can be attributed to Bragg-type crystallite sites embedded in a material with refractive index n.
Abstract: Optical scattering data have been used to investigate molecular order in certain cholesteric mixtures. When films of these materials are deposited on a reflecting substrate, their colors can be shifted by several thousand angstroms for any condition of illumination and observation by a mechanical disturbance. The dispersive color reflections in both the undisturbed and disturbed films can be attributed to Bragg‐type crystallite sites embedded in a material with refractive index n. When the films are mounted on a reflective substrate, there are effectively two angles of incidence. One angle corresponds to the actual angle of incidence and the other angle corresponds to the reflected beam. Accordingly, for some fixed combination of incidence and observation angles, two wavelength peaks should be observed for an isotropic distribution of scattering sites. Scattering data in both reflection and transmission indicate that the distribution is far from isotropic and that the effect of disturbance is to reorient ...