Showing papers on "Light scattering published in 1973"

The quantum theory of light

Abstract: Preface 1. Planck's radiation law and the Einstein coefficients 2. Quantum mechanics of the atom-radiation interaction 3. Classical theory of optical fluctuations and coherence 4. Quantization of the radiation field 5. Single-mode quantum optics 6. Multimode and continuous-mode quantum optics 7. Optical generation, attenuation and amplification 8. Resonance fluorescence and light scattering 9. Nonlinear quantum optics Index

The theory of diffuse X-ray scattering and its application to the study of point defects and their clusters

Abstract: The theory of the diffuse scattering by point defects and by defect clusters is reviewed. For a small concentration of statistically distributed point defects the symmetry of the long ranging part of the displacement field and the strength of the defects can be obtained from scattering measurements close to the reciprocal lattice points (Huang scattering). In addition to the (symmetrical) Huang scattering an asymmetry of the scattering is observed. For defects with sufficiently large displacements, the sign of this asymmetric scattering determines the sign of the displacement field around the defect and its magnitude yields information about the magnitude of the displacements close to the defect. For defect clusters the diffuse scattering is strongly modified. The Huang scattering very near to the Bragg reflection increases in direct proportion to the number of point defects in the cluster. For larger distances q from the Bragg reflection the intensity decreases as 1/q4.

Multi-color semiconductor lamp

Abstract: A multi-color semiconductor lamp comprising a plurality of light emitting diodes disposed close to one another and respectively emitting the light of different colors and a light scattering layer covering these light emitting diodes. With this device, light emitted from any one of the plurality of light emitting diodes is visible as if it were emitted from one and the same position. The present invention therefore, makes it possible to obtain clear multi-color indication with a small-size lamp which has heretofore been difficult.

On the possibility of measuring gas concentrations by stimulated anti‐Stokes scattering

Abstract: A novel and very sensitive method for gas concentration measurements is proposed. Intense light scattering is obtained through a stimulated interaction. The method appears more practical than spontaneous Raman scattering for gas flow analysis with fine spatial resolution. Experimental results with the detection of H2 are given.

Rayleigh scattering

Abstract: By using a computer program, the authors intend to compute quantities specifying the low frequency scattering behavior of rotationally symmetric bodies which are metallic (electromagnetic scattering), soft, or hard (acoustic scattering)

The quantum theory of light.

Abstract: Preface 1. Planck's radiation law and the Einstein coefficients 2. Quantum mechanics of the atom-radiation interaction 3. Classical theory of optical fluctuations and coherence 4. Quantization of the radiation field 5. Single-mode quantum optics 6. Multimode and continuous-mode quantum optics 7. Optical generation, attenuation and amplification 8. Resonance fluorescence and light scattering 9. Nonlinear quantum optics Index

A new polarization‐modulated light scattering instrument

Abstract: A new light scattering instrument is described for measuring, as a function of scattering angle, the elements of the matrix describing light scattered from small particle systems. The instrument uses a piezo‐optical birefringence modulator to modulate the polarization state of the incident light beam, and uses lock‐in amplifier detection of the scattered light. The first and second harmonics of the modulation frequency are used with various combinations of filters and orientations to give the separate matrix elements. A treatment of a simple scattering experiment by means of Mueller calculus is carried through to illustrate the interactions of the light with the scattering system and with the various components of the measuring instrument. Evaluation of the instrumental performance is shown through measurements on two systems of monodisperse polystyrene spheres of average radius 550 and 3940 A, compared with Mie calculations. Further measurements on sulfur colloids are presented, and suggestions of the va...

Depolarized Rayleigh scattering and orientational relaxation of molecules in solution. I. Benzene, toluene, and para‐xylene

Abstract: Measurements of orientational relaxation rates of benzene, toluene, and para‐xylene in a variety of solvents have been made by depolarized light scattering. A plot of reorientational relaxation time of each solute versus solution viscosity was found to fit a straight line with nonzero intercept. The slopes of the lines are compared with those predicted by the Stokes‐Einstein relation.

Wave‐length dependencies of light scattering in normal and cold swollen rabbit corneas and their structural implications

Abstract: 1. The studies described herein involve the use of light scattering measurements to characterize the ultrastructural arrangement of the constituent collagen fibrils in rabbit corneal stromas. 2. Theoretical light scattering techniques for calculating the scattering to be expected from the structures revealed by electron micrographs are discussed, and comparison with the experimental light scattering tests the validity of these structures. 3. The wave-length dependence of light transmission and of angular light scattering from normal corneas is in agreement with the short range ordering of collagen fibrils depicted in electron micrographs. 4. The transmission measurements on oedematous rabbit corneas indicate that transmission decreases linearly with the ratio of thickness to normal thickness. 5. The wave-length dependence of transmission through cold swollen corneas indicates that the increased scattering is caused by large inhomogeneities in the ultrastructure. Electron micrographs do, indeed, reveal the presence of such inhomogeneities in the form of large regions completely devoid of fibrils.

Light Scattering of Stiff Chain Polymers

Abstract: The angular distribution of scattered light (or the particle scattering factor) of the stiff chain polymers is calculated by assuming an appropriate Fourier transform of the distribution function of this polymer chain. For very small and very large scattering angles the result is respectively reduced to the forms of the Debye's scattering factor for random coil chain and to that for rigid rod molecule. By assuming that the polymer chain expansion by intramolecular forces is uniform, but the contour length is kept as constant the excluded volume effect on the angular distribution is calculated. The result shows that the transition point of scattering curve which gives a boundary between random coil- and rigid rod-scatterings is inversely proportional to the square of molecular expansion coefficient. This is in qualitative agreement with the recent experimental results by Wada and other. An approximate distribution function which gives the correct second and fourth moments of the chain end to end distance i...

Light scattering from dilute macromolecular solutions

Abstract: The polarized light scattering spectrum from a dilute solution of spherical macromolecules is customarily interpreted on the basis of independent particle diffusion. However, it is known that diffusion in such a system is governed by a many particle diffusion equation with cross‐diffusion coefficients Dij that depend on the inverse distance between all pairs of particles (i, j). Here we prove that the spectrum from the system described by the N‐particle diffusion equation is identical to the spectrum obtained from the simple, but incorrect, independent particle diffusion model. The physical reason for this suprising simplication is that the Dij are proportional to Oseen's tensor which holds for an incompressible fluid and hence has no longitudinal part. When short‐range forces are taken into account as well as the long‐range hydrodynamic interaction present in Dij, it is possible to obtain simple approximate expression for a k‐dependent effective diffusion constant Deff(k). This expression is evaluated fo...

The Effect of Temperature and Pressure on the Refractive Index of Some Oxide Glasses.

Abstract: The change in refractive index with temperature has been determined for some oxide glasses from about -200 to 700 °C. The change in refractive index with applied hydrostatic pressure has been determined at room temperature from a pressure of 105 to 108 Pa. All measurements were made using the yellow spectral line of helium. A calcium aluminate glass, an aluminum magnesium phosphate glass, a binary barium borate glass and a multicomponent germanate glass were studied, as were four commercial specimens of fused silica. From the data at room temperature, it has been possible to calculate the change in electronic polarizability with temperature at constant volume. This parameter has been found to be very high for the glasses as compared to crystals, and this agrees with the results of earlier research on silica-based optical glasses. Furthermore, over the entire temperature range, the change of refractive index with temperature is shown to be due predominantly to the temperature dependence at constant volume of the electronic polarizability. The relevance of the data to the molecular scattering of light in glasses is discussed.

Low angle laser light scattering-absolute calibration.

Abstract: A new method for the calculation of the Rayleigh factor from low angle light scattering measurements is developed. This method does not require a uniform intensity illuminating beam, hence efficiently utilizes all the beam from a focused laser source. Scattering volume is then very small, reducing sample volume and interference from contaminant particles. All the parameters necessary for the calculation of the Rayleigh factor (including the exact dependence on sample refractive index) are measurable, hence absolute calibration is possible. Over-all error is estimated to be less than 2.3% under specified conditions. Measurements are possible at scattering angles as small as 2° obviating the need for angular extrapolations in the determination of molecular weight of most dissolved samples. Rayleigh factors at 22°C, 633 nm, and a scattering angle of 4° for water, methanol, benzene, and toluene, were found to be, respectively, 0.907, 2.56, 12.15, and 13.45 × 10−6 cm−1.

Rayleigh scattering: Orientational motion in highly anisotropic liquids

Abstract: Light scattering studies of the depolarized Rayleigh line are reported for liquid benzene over the temperature range +13 to 76°C and for other substituted benzenes. Values of the 〈 P2(o)P2(t)〉 and 〈 Ṗ2(o)Ṗ2(t)〉 correlation functions calculated from these spectra show considerable free rotor behavior (∼ 15° steps) and incomplete loss of memory after collision. Further consideration of the 〈 Ṗ2(o)Ṗ2(t)〉 correlation allows calculation of the angular velocity correlation function. The time between collisions, τBC, is also obtained and found to be in good agreement with a ``moveable wall'' cell model. It is proposed that the ``shoulder'' noted in the wings of many anisotropic liquids is caused by incomplete loss of memory after collision.

Experimental Differential Light-Scattering Correction to the Circular Dichroism of Bacteriophage T2

Abstract: Experimental techniques are presented that can be used to assay and correct for differential light scattering effects in circular dichroism spectra of biological macrostructures. The assay is based upon use of variable detector geometries that collect light over large solid angles. Disrupted T2 virus suspensions and purified T2 phage DNA exhibit geometry-independent spectra; the spectrum of intact T2 virus is highly sensitive to detection geometry. On the basis of spectra obtained after light-scattering correction, the structure of T2 DNA in the phage particle is assigned to the C form. We conclude that: (i) The measured circular dichroism of a light-scattering specimen may be highly sensitive to light-detection geometry of the instrument. This effect is indicative of differential scattering intensity for left and right circularly polarized light. (ii) Some optically active particles, although they scatter light intensely, exhibit circular dichroism that is independent of detection geometry and, therefore, apparently uninfluenced by differential light scattering. We infer that whether differential light scattering arises may depend upon the presence or absence of ordered asymmetry in the organization of the scattering particle. (iii) The circular dichroism of any light-scattering specimen should be measured again in apparatus designed for differential light-scattering correction as a prerequisite to meaningful structural conclusions. (iv) Differential scattering effects in circular dichroism may be potentially useful as a probe for large-order organization of the scattering particle.

Molecular Order and Surface Tension for the Nematic-Isotropic Interface of MBBA, deduced from Light Reflectivity and Light Scattering Measurements

Abstract: Light reflectivity measurements show that the molecules of MBBA lie parallel to the nematic-isotropic interface, that their orientations in the absence of any external field are correlated in the plane of the interface over distances greater than the optical wavelength and allow a study of the dynamics of the effect of a magnetic field on these molecules. The spectrum analysis of the light scattered by the interface yields the value of the surface tension. This experimental value is used to estimate the correlation length in the isotropic phase.

Application of Backus-Gilbert Inversion Technique to Determination of Aerosol Size Distributions from Optical Scattering Measurements

Abstract: The inversion technique of Backus and Gilbert is applied to the determination of size distributions of spherical particles from optical scattering measurements. The spatial resolution inherent in a set of multiwavelength measurements is studied as a function of number of measurements, measurement noise level, and radius. The inversion technique is then applied to computer simulated intensity data to recover size distributions. These examples indicate that the distribution can be recovered at selected points without using a priori assumptions about the shape of the distribution.

Spectrum of Light Scattering from Thermal Shear Waves in Liquids

Abstract: A depolarized doublet centered at the frequency of the exciting laser radiation has been observed in the light-scattering spectrum of several liquids, including nitrobenzene, aniline, quinoline, and $m\ensuremath{-}\mathrm{nitrotoluene}$ The frequency separation, line shape, and polarization characteristics suggest that this doublet arises from thermally excited shear waves in these relatively viscous liquids

Studies in molecular dynamics. XII. Band shape of the depolarized light scattered from atomic fluids

Abstract: The induced dipole‐induced dipole autocorrelation functions for systems of atom interacting with Lennard‐Jones, hard‐sphere, and square‐well potentials are presented. No evidence for long‐time power‐law tails on these functions is found. The band shapes calculated from the autocorrelation functions agree quantitatively with the available data on the band shapes of depolarized light scattering of atomic systems over an enormous range of temperature and density. The calculated results vary with the potential especially at high densities, and the agreement with experiment is within the uncertainty in the true atomic potential. This is true in spite of the earlier findings that the intensities calculated in this way are an order‐of‐magnitude too large at normal liquid densities because the calculations neglect the distortion of the polarizability of the individual atoms.

Two component mie scattering models of sargasso sea particles.

Abstract: The volume scattering function is calculated for particle suspensions consisting of two components systematically distributed in a manner consistent with Coulter Counter observations in the Sargasso Sea. The components are assigned refractive indices 1.01-0.01i and 1.15 to represent organic and inorganic particles, respectively. The only models found that reproduce observed scattering functions require a considerable fraction of the suspended particle volume to be organic in nature. This fraction, however, contributes less than 10% to the total scattering function. The model finally chosen indicates that the inorganic particles smaller than 2.5 micro do not occur in large enough concentrations to have a significant effect on the volume scattering function.

Measured Light-Scattering Properties of Individual Aerosol Particles Compared to Mie Scattering Theory

Abstract: Monodispersed spherical aerosols of 0.26–2-μ diameter with approximate range of indexes of refraction of atmospheric aerosols have been produced in the laboratory by atomization of liquids with a vibrating capillary. Integrated light scattered 8 through 38 degrees from the direction of forward scattering has been measured with a photoelectric particle counter and compared to Mie theory calculations for particles with complex indexes of refraction 1.4033–0i, 1.592–0i, 1.67–0.26i, and 1.65–0.069i. The agreement is good. The calculations take into account the particle counter white light illumination with color temperature 3300 K, the optical system geometry, and the phototube spectral sensitivity. It is shown that for aerosol particles of unknown index of refraction the particle counter size resolution is poor for particle size greater than 0.5μ, but good for particles in the 0.26–0.5-μ size range.

Laser light scattering in fluid systems

Abstract: Generalized hydrodynamics suggests that at high frequencies, there should be significant departire from classical hydrodynamics behavior in simple fluids. In particular, the frequency dependence of transport coefficients is not negligible and should introduced observable effects into the propagation of hyper-sound. This work which analyzes rayleigh-Brillouin spectra measured in liquid Argon and Neon reports one of the first experimental investigations of generalized hydrodynamic behavior in simple liquids