Showing papers on "Light scattering published in 1968"
TL;DR: Two optical techniques—light scattering and birefringence—have been used to detect rapid structural changes accompanying the action potentials in two types of non-myelinated nerve fibre.
Abstract: Two optical techniques—light scattering and birefringence—have been used to detect rapid structural changes accompanying the action potentials in two types of non-myelinated nerve fibre. Changes in light scattering originate from at least two different phenomena, while a large part of the birefringence change seems to be directly dependent on the potential difference across the axon membrane, and arises in radially oriented molecules associated with the membrane.
443 citations
TL;DR: In this paper, the theory of light scattering by one-and two-magnon excitations is presented and compared with the experimental results in the tetragonal antiferromagnets Mn${\mathrm{F}}{2}$ and Fe${F}_{2h}12}$.
Abstract: We present details of the theory of light scattering by one- and two-magnon excitations, and compare predictions of the theory with our experimental results in the tetragonal antiferromagnets Mn${\mathrm{F}}_{2}$ and Fe${\mathrm{F}}_{2}$. Two mechanisms are considered for first-order (one-magnon) light scattering: one involving a direct magnetic-dipole coupling and the other involving an indirect electric-dipole coupling which proceeds through a spin-orbit interaction. Experimental results on the intensity and polarization selection rules of the first-order scattering show that the spin-orbit mechanism is the important one. On the other hand, second-order (two-magnon) scattering is observed to be even stronger than first-order scattering in these antiferromagnets, implying that the process is not due to the spin-orbit mechanism taken to a higher order in perturbation theory. A theory of second-order scattering based on an excited-state exchange interaction between opposite sublattices is given. When coupled with group-theoretical requirements for the ${{D}_{2h}}^{12}$ crystals, the mechanism predicts the intensity, the polarization selection rules, and the magnetic field dependence of the second-order spectrum. Features of the second-order spectra are related quantitatively to magnons at specific points in the Brillouin zone. Analysis of both first- and second-order magnon scattering has thus enabled determination of the complete magnon dispersion relation for Fe${\mathrm{F}}_{2}$.
441 citations
01 Jul 1968
TL;DR: In this article, a new electrooptic effect in certain classes of nematic liquid crystals is presented, termed "dynamic scattering" because scattering centers are produced in the transparent, anisotropic medium due to the disruptive effects of ions in transit.
Abstract: A new electrooptic effect in certain classes of nematic liquid crystals is presented. The effect has been termed "dynamic scattering" because scattering centers are produced in the transparent, anisotropic medium due to the disruptive effects of ions in transit. The ions can be produced by field assisted dissociation of neutral molecules and/or Schottky emission processes. The rise times of 1 to 5 ms and decay times of less than 30 ms, together with dc operating voltages in the 10 to 100 V range, make dynamic scattering seem attractive for such applications as alphanumeric indicators, and do not preclude its use in line-at-a-time matrix addressed, real-time displays. Reflective contrast ratios of better than 15 to 1 with efficiencies of 45 percent of the standard white have been demonstrated.
423 citations
TL;DR: Although a mathematically rigorous inversion procedure seems impractical at this time, the use of detailed differential scattered intensity data as an identification fingerprint shows considerable promise.
Abstract: Differential light scattering techniques appear to represent an attractive physical method for the rapid identification of various microorganisms. Certain general results of inverse scattering theory suggest strongly that characteristic of each distinct microorganism that scatters light is an essentially unique scattering pattern, i.e., unique differential scattered intensity and polarization. Although a mathematically rigorous inversion procedure seems impractical at this time, the use of detailed differential scattered intensity data as an identification fingerprint shows considerable. promise. Published measurements on nonbiological scatterers confirm this possibility. A variety of calculations are presented that contrast the expected scattering characteristics of certain microorganisms such as Bacillus subtilis, B. anthracis, Staphylococcus epidermidis, S. aureus, Escherichia coli, and the spores of B. megaterium and B. cereus. Experimental and instrumentation difficulties and possible procedures are discussed. A review and laboration of some applicable features of Rayleigh-Gans scattering are included as an appendix.
185 citations
TL;DR: The numerous small angle scatterings of the photon in the direction of the incident beam are followed accurately and produce a greater penetration into the cloud than is obtained with a more isotropic and less realistic phase function.
Abstract: Visible light scattering by clouds calculated by photon multiple scattered path following Monte Carlo code, using Mie theory
175 citations
TL;DR: In this article, the spectral distribution of light scattered from an infinitely dilute solution of monodisperse, optically isotropic, rigid rods is investigated, and the contributions to the total scattered intensity of terms dependent on the rotational diffusion coefficient are calculated as a function of the product of lengths of the rod and the scattering vector.
Abstract: The spectral distribution of light scattered from an infinitely dilute solution of monodisperse, optically isotropic, rigid rods is investigated. The contributions to the total scattered intensity of terms dependent on the rotational diffusion coefficient are calculated as a function of the product of lengths of the rod and the scattering vector. It is found that rotational diffusion contributions become important in scattering from long rods at large scattering angles.
157 citations
TL;DR: A calculation of the angular dependence of light scattering from wormlike chains with excluded volume effects is reported, demonstrating that the same values of excluded volume parameter and statistical segment length which explain the sedimentation and viscosity behavior of DNA also account satisfactorily for the scattering behavior.
Abstract: This paper reports a calculation of the angular dependence of light scattering from wormlike chains with excluded volume effects. The Daniels distribution function, modified for excluded volume effects, is used to compute averages for scattering elements separated by contour lengths which are long with respect to the persistence length of the chain. An expansion in terms of exactly known moments of the distribution for the wormlike coil without excluded volume is used for short contour lengths. The results are applied to scattering from calf thymus (M = 18.1 × 106) and T7 (M = 25.4 × 106) DNA. It is demonstrated that the same values of excluded volume parameter (e = 0.11) and statistical segment length (1/λ′ = 900 A) which explain the sedimentation and viscosity behavior of DNA also account satisfactorily for the scattering behavior. Molecular weights and root-mean-square radii estimated by extrapolation from scattering data obtained in the angular region from 10° to 25° will be 5–10% too large for DNA of molecular weight 20 × 106–30 × 106.
154 citations
TL;DR: In this paper, light scattering attributable to a change in polarizability produced in colliding pairs of atoms was observed in gaseous Ar and Kr. The experimental results were qualitatively accounted for by relations between the integrated intensity and the collision-induced polarization.
Abstract: Light scattering attributable to a change in polarizability produced in colliding pairs of atoms is observed in gaseous Ar and Kr. The experimental results are qualitatively accounted for by relations between the integrated intensity and the collision-induced polarizability.
136 citations
TL;DR: Curves are given of the reflected and transmitted radiances and polarizations for both the haze and cloud models and for several solar angles, optical thicknesses, and surface albedos.
Abstract: Radiance and polarization of multiple scattered light from haze and clouds calculated from Stokes vectors by Monte Carlo method
TL;DR: For suspension of randomly oriented, asymmetric particles of slightly irregular shape, reasonably accurate estimates of the light scattering can be computed from simple Rayleigh-Gans theory, even when applied to large objects such as mammalian mitochondria or the most-studied bacteria, Escherichia coli.
TL;DR: Theories of absorption and scattering of light due to electric origins by magnetic crystals are surveyed in this article, where the spin-dependent electric polarizability and a general expression for the scattering intensity are discussed systematically.
Abstract: Theories of absorption and scattering of light due to electric origins by magnetic crystals are surveyed. Electric dipole moments associated with ionic spins are discussed from symmetry point of view. Two‐magnon absorptions are treated by using this spin‐dependent electric dipole moment. Relative importance of various possible mechanisms giving rise to this moment are discussed. Light scattering by spin systems is treated by using the spin‐dependent electric polarizability and a general expression is given for the scattering intensity. Symmetry properties and microscopic mechanisms of this polarizability are discussed systematically. One‐ and two‐magnon scatterings as well as critical scatterings by spin systems are discussed in terms of this theory. Discussions are also extended briefly to the case of magnon‐phonon absorption and the magnon sidebands or the magnon‐exciton absorptions.
TL;DR: In this article, Rayleigh scattering from atoms and molecules in the gaseous state at 1-atm pressure was measured using a Q-switched ruby laser of 8MW average power and care in minimizing spurious light.
Abstract: Measurements of Rayleigh scattering from atoms and molecules in the gaseous state at 1-atm pressure are described. The use of a Q-switched ruby laser of 8-MW average power and care in minimizing spurious light permitted the determination of very small depolarizations. No depolarization could be detected in the scattering from argon and helium. However, finite depolarization ratios ρν (for vertically polarized incident light) were measured for xenon and methane: 1.55(±0.25) × 10−4 and 1.27 (±0.23) × 10−4, respectively. Departures from ideal-gas behavior provide the most plausible explanation for these findings.Depolarization ratios were also measured in hydrogen, deuterium, nitrogen, and nitrous oxide, and were found to be lower than generally accepted values. Measured differential-scattering cross sections at 60° for He, Ar, Xe, CH4, H2, D2, N2, and N2O were within experimental error of values calculated from known indices of refraction. The angular dependence of Rayleigh scattering in N2 as a function of the polarization states of both incident and scattered radiation was studied from 30° to 150°, and was found to be in agreement with theory.
TL;DR: In this article, the focused beam of an argon-ion laser was used as a light source for Raman-scattering experiments in gases, and photoelectric recording of rotation-vibration Raman spectra was observed from about 1011 gas molecules in the focal region of the laser beam.
Abstract: The focused beam of an argon–ion laser was used as a light source for Raman-scattering experiments in gases. Photoelectric recording of rotation–vibration Raman spectra has been observed from about 1011 gas molecules in the focal region of the laser beam. The focusing geometry used to illuminate the gas samples is discussed and the important parameters of the optical system for collecting the Raman-scattered light from the small volumes are considered. The pulse-counting detection system is described and the new experimental results are presented.
TL;DR: Polarizing glasses were made by stretching glass containing colloidal silver and the position of the absorption bands depends strongly on the elongation, which seems to be consistent with the predictions of the theory of light absorption by small metal particles based on a free electron model.
Abstract: Polarizing glasses were made by stretching glass containing colloidal silver. The position of the absorption bands depends strongly on the elongation. This dependence seems to be consistent with the predictions of the theory of light absorption by small metal particles based on a free electron model.
TL;DR: In this article, the possibility of using stimulated Compton scattering for obtaining laser action was considered and the advantages of a Compton laser are that it is voltage tunable over a wide frequency range and may provide intense, coherent radiation in portions of the spectrum where other sources are not readily available.
Abstract: Consideration is given to the possibility of using stimulated Compton scattering for obtaining laser action. The advantages of a Compton laser are that it is voltage tunable over a wide frequency range and may provide intense, coherent radiation in portions of the spectrum where other sources are not readily available. It is found that appreciable gain exists at far infrared wavelengths.
TL;DR: In this paper, multiple scattering by large particles in optically thick layers, using scalar transfer equations, was used to solve the problem of multiple scattering of large particle in optical layers.
Abstract: Multiple scattering by large particles in optically thick layers, using scalar transfer equations
TL;DR: A new method is proposed for determining the effects of internal particle structure on observable light fluxes and it is found that when a particle becomes less homogeneous, large angle scattering should increase and small angle scatteringShould decrease.
TL;DR: Experimental measurements show that the Rayleigh-Gans approximation for calculating the intensity of scattered light at angles up to 30° applies surprisingly well to particles as large as bacteria, and it is proposed that low angle light scattering can be useful in estimating the average volume of the bacterial cells in populations.
TL;DR: 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 $m\ensuremath{-}\mathrm{nitrotoluene}$ as mentioned in this paper.
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.
TL;DR: In this paper, the forward particle scatterance was found to be virtually independent of wavelength, whereas the backward scatterance is dependent on the wavelength, and the ratio of scatterance at 45° to total scatterance over all angles was found within narrow limits for different oceanic areas.
01 Oct 1968
TL;DR: In this paper, the integral for the average scattered power from a rough surface obtained from physical optics is shown to be proportional to the joint probability density function for the surface slopes in the high-frequency limit.
Abstract: The integral for the average scattered power from a rough surface obtained from physical optics is shown to be proportional to the joint probability density function for the surface slopes in the high-frequency limit.
TL;DR: In this article, a set of equations derived to describe the optics of highly scattering materials are explained, extended, and applied to the problem of in vitro and in vivo measurement of the relative oxygen saturation of nonhemolyzed blood.
Abstract: A set of equations derived to describe the optics of highly scattering materials are explained, extended, and applied to the problem of in vitro and in vivo measurement of the relative oxygen saturation of nonhemolyzed blood. Fundamental absorption and scattering coefficients are described and related to the absorption coefficient of hemolyzed blood. Diffusion equations for light photons are used to solve the scattering problem in a three-dimensional system that may be useful for in vivo oxyhemoglobin measurements. Crude application to published data from in vitro measurements on nonhemolyzed blood indicates that the scattering coefficient of whole blood is probably not very wavelength-dependent.