Showing papers on "Light scattering published in 1983"

Absorption and Scattering of Light by Small Particles

Abstract: BASIC THEORY. Electromagnetic Theory. Absorption and Scattering by an Arbitrary Particle. Absorption and Scattering by a Sphere. Particles Small Compared with the Wavelength. Rayleigh--Gans Theory. Geometrical Optics. A Potpourri of Particles. OPTICAL PROPERTIES OF BULK MATTER. Classical Theories of Optical Constants. Measured Optical Properties. OPTICAL PROPERTIES OF PARTICLES. Extinction. Surface Modes in Small Particles. Angular Dependence of Scattering. A Miscellany of Applications. Appendices. References. Index.

Molecular Light Scattering and Optical Activity

Abstract: Ranging from the physics of elementary particles to the structure of viruses, the subject matter of this book stresses the importance of optical activity and chirality in modern science and will be of interest to a wide range of scientists. Using classical and quantum methods with a strong emphasis on symmetry principles, the volume develops the theory of varied optical activity and related phenomena from the perspective of molecular scattering of polarized light. First Edition Hb (1983): 0-521-24602-4

Anharmonic effects in light scattering due to optical phonons in silicon

Abstract: Systematic measurements by light scattering of the linewidth and frequency shift of the $\stackrel{\ensuremath{\rightarrow}}{\mathrm{q}}=0$ optical phonon in silicon over the temperature range of 5-1400 K are presented. Both the linewidth and frequency shift exhibit a quadratic dependence on temperature at high temperatures. This indicates the necessity of including terms in the phonon proper self-energy corresponding to four-phonon anharmonic processes.

Electromagnetic scattering by magnetic spheres

Abstract: A number of unusual electromagnetic scattering effects for magnetic spheres are described. When ∊ = μ, the backscatter gain is zero; the scattered radiation is polarized in the same sense as the incident radiation. In the small-particle (or long-wavelength) limit, conditions are described for zero forward scatter, for complete polarization of scattered radiation in other directions, and for asymmetry of forward scatter to backscatter. The special case in the small-particle limit of m = 1, i.e., μ = 1/∊, provides interesting special instances of complete polarization and forward-scatter-to-backscatter asymmetry.

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 Monte Carlo model for the absorption and flux distributions of light in tissue

Abstract: A Monte Carlo computer model has been developed to study the propagation of light in tissues. Light attenuation is assumed to result from absorption and isotropic scattering. The model has been used to predict the distribution of absorbed dose in homogeneous tissues of different absorption/scattering ratios, for illumination both by external light beams and via implanted optical fibers. The photon flux into optical fibers placed in the tissue as detectors has also been investigated. The results are interpreted in relation to the use of visible light irradiation for photo radiation therapy.

Scattering and absorption of turbid materials determined from reflection measurements. 1: theory.

Abstract: To allow the determination of scattering and absorption parameters of a turbid material from reflection measurements the relation of these parameters to the reflection has been described by two theoretical approaches. One approach is based on the diffusion theory which has been extended to include anisotropic scattering. This results in a reflection formula in which the scattering and absorption are described by one parameter each. As a second more general approach a Monte Carlo model is applied. Comparison of the results indicates the range of values of the scattering and absorption parameters where the computationally fast diffusion approach is applicable.

The enhancement of Raman scattering, resonance Raman scattering, and fluorescence from molecules adsorbed on a rough silver surface

Abstract: The enhancements of normal Raman scattering, resonance Raman scattering, and fluorescence from molecules adsorbed on identical, well‐characterized, silver‐island films are reported. The enhancement arises from the electromagnetic interaction between the molecules and the electronic plasma resonance of the silver islands. A hierarchy of enhancement ratios is found, with typical values of 105 for RS, 103 for RRS and 10−1 to 10 for fluorescence, depending on the quantum yield of the molecular fluorescence. A model, developed on heuristic grounds and substantiated using the density matrix formalism, describes the light scattering processes and the effects of the plasma resonance. This model presents a unified picture of the surface‐induced enhancement effects and is consistent with the experimental values. The comparison of all the forms of optical scattering leads to a complete determination of the role of the plasma resonances in the various portions of the scattering process. The excitation of the electronic plasma resonance results in an increased local field at the molecules leading to an increased excitation or absorption rate. Similarly, the excitation of the plasma resonance by the molecular emission dipole results in an increase in the radiative decay rate. However, the electromagnetic coupling of the molecule to the plasma resonance also adds an additional damping channel which can result in a reduction of the absorption or excitation rate as well as the emission yield. The resultant balance of these processes leads to the hierarchy in the measured enhancements. The hierarchy of enhancements is also shown to have important spectroscopic consequences.

High spectral resolution lidar to measure optical scattering properties of atmospheric aerosols. 1: Theory and instrumentation

Abstract: A high spectral resolution lidar technique to measure optical scattering properties of atmospheric aerosols is described. Light backscattered by the atmosphere from a narrowband optically pumped oscillator-amplifier dye laser is separated into its Doppler broadened molecular and elastically scattered aerosol components by a two-channel Fabry-Perot polyetalon interferometer. Aerosol optical properties, such as the backscatter ratio, optical depth, extinction cross section, scattering cross section, and the backscatter phase function, are derived from the two-channel measurements.

Enhanced light reflection by dye monolayers at the air–water interface

Abstract: The reflection of light from an air–water interface is enhanced by dye containing monolayers in the spectral region of the dye absorption. The intensity of the reflected light depends linearly on the density of chromophores in the mixed monolayer. From the measurement of both absorption and reflection spectra of a dye containing monolayer the damping constant of coherent light scattering can be estimated. The value of the reflection measurement for the investigation of adsorption processes and the control of monolayer organization is demonstrated.

Magnetic excitations in layered media: Spin waves and the light-scattering spectrum

Abstract: We present an analysis of the spin-wave spectrum of a semi-infinite stack of ferromagnetic films, each of which is separated by a gap filled by a nonmagnetic medium. This is done within a formalism which includes the Zeeman and dipolar contributions to the spin-wave energy, with exchange omitted. We then calculate the spin-wave contribution to the Brillouin spectrum of such a system, in the backscattering geometry. The aim is to compare the spectrum for scattering from a sample with this geometry, with that from an isolated film. Two features unique to the stack appear in the spectrum. Each film, in isolation, possesses surface spin waves on its boundaries (Damon-Eshbach waves). In the layered geometry these interact to form a band of excitations of the array, which has nonvanishing component of wave vector normal to the stack. We find a feature in the spectrum associated with scattering from this band of modes; the position of the peak is controlled by dispersion introduced by interfilm interactions. Under certain conditions, the semi-infinite stack possesses a surface spin wave, whose eigenfunction is a linear superposition of individual film states, with amplitude that decays to zero as one moves down into the stack interior. This mode also produces a distinct feature in the light-scattering spectrum. These points are illustrated with a series of calculations of the spectrum, for parameters characteristic of layered ultrathin coherent structures.

Simultaneous determination of refractive index and size of spherical dielectric particles from light scattering data.

Abstract: The diameter and refractive index of micrometer sized spherical dielectric particles are simultaneously deduced using the wavelength dependence of backscattering data from optically levitated particles. The accuracy of the results is set by experimental errors in the determination of the wavelength of backscatter resonance peaks and the ratio of slopes of specified peaks. At present the refractive index and diameter can be deduced with relative errors of 5 x 10(-5). This represents the most accurate determination of absolute size and refractive index yet made by light scattering. A reduction of these errors by an order of magnitude is possible. We assume a priori knowledge of diameter and refractive index with accuracy of 10(-1) and 5 x 10(-3), respectively.

Resonance Rayleigh scattering of cyanine dyes in solution

Abstract: Every process of light absorption is inherently associated with a resonance scattering of the incident beam regardless of the nature of the absorbing molecules. Both the real and imaginary parts of the refractive index contribute to the resonance scattering, and marked depolarization is expected to be observed as a rule in the light scattered by complex molecules. The resonance and near‐resonance Rayleigh scattering has been measured for a number of cyanine dyes: pseudocyanine, orthochrome T, 1,1′‐diethyl‐2, 2′‐pyridyl‐quinolyl cyanine, and pinacyanol chloride, in a number of solvents. In no case was the measured scattering intensity weaker than that expected theoretically, and good agreement between theory and experiment was found as a rule at the blue part of the absorption bands. In contrast, the measured scattering intensities exceeded (by up to fourfold) the theoretically expected values at the red parts of the absorption bands. Possible reasons for this discrepancy are discussed.

Scattering and absorption of turbid materials determined from reflection measurements. 2: measuring method and calibration.

Abstract: A new experimental method has been developed to determine the scattering and absorption characteristics of a turbid material. Existing methods usually require transmission and reflection measurements carried out on a thin slab of the material under study; this method is based on reflection measurements carried out on bulk material. This will be of great advantage in many applications. This paper describes the measuring system and indicates the area of application of the method. Calibration measurements have been carried out to substantiate the approach.

Light gradients in plant tissue

Abstract: In this paper we suggest a method for calculating light gradients in scattering and absorbing media. The method is based on the Kubelka-Munk theory and involves computational modeling of light fluxes in a multilayered object, when every layer satisfies the prerequisites of the Kubelka-Munk theory. The model also includes specular reflection that may contribute strongly to internal photon fluence rates for diffuse light. To illustrate the possible effects of light gradients, a cotyledon of Cucurbita pepo is described in terms of this model. It is argued that a number of results in in vivo spectroscopy cannot be correctly interpreted unless light gradients or optics in general are included in the discussion, i.e., the light flux at the site of the pigment has to be known. To outline the difficulties involved some methods of measuring light gradients or internal photon fluence rates are critically considered.

Response Characteristics of the Particle Measuring Systems Active Scattering Aerosol Spectrometer Probes

Abstract: Predictions of the size response of various light-scattering aerosol counters manufactured by Particle Measuring Systems are reported. Models that exploit the high intensity of light available within the cavity of a He-Ne gas laser (generically referred to by the manufacturer as ''active scattering aerosol spectrometer probes'') are considered. The new response function properly averages over particle trajectories through nodes, antinodes, and intermediate regions of the intracavity laser beam. Our studies address probes having two basic scattering geometries: those that collect light scattered over a relatively narrow solid angle (subtending angles between 4° and 22° from the laser beam axis, as in the model ASASP-300 and ASASP-300X probes) and those that collect light over a rather large solid angle (between 35° and 120° , as in the ASASP-X, ASASP-100X, LAS-250X, LAS-X, and HS-LAS probes). The theoretical response predictions for both narrow-angle and wide-angle probes are compared to previous measureme...

Scattering of laser beams and the optical potential well for a homogeneous sphere

Abstract: A theory is developed for the scattering of a fundamental-mode laser beam by a homogeneous sphere located in the beam passage. The expression for the incident laser beam is obtained by using the complex-source-point method, and the light-field distributions inside and outside the sphere are given. The formulas for the energies scattered and absorbed by the sphere and for the radiation pressure exerted on the sphere are derived, and their qualitative features are discussed. Results of numerical calculation of the radiation pressure and their physical interpretations are presented. All the analytical formalism is generalized for immediate treatment of the scattering of higher-order Hermite–Gaussian-mode laser beams by a homogeneous sphere.

Turbidimetric determination of particle size distributions of colloidal systems

Abstract: Application of the Mie theory of light scattering to measurements of the turbidity ratio and the wavelength exponent provides an easy method for estimating particle size distributions of nonabsorbing isotropic spheres in the micrometer to submicrometer range. Combining both these lightscattering techniques not only allows one to analyze particle sizes which are too large for quasi-elastic light scattering and too small for optical microscopy, but can be accomplished with only two turbidity measurements and no prior knowledge of the particle volume fraction. An algorithm is presented for constructing turbidity spectra, for any system of known optical constants and known distributional form, which can be used to easily determine the mean diameter and standard deviation of an unknown distribution. Using this algorithm, size-distribution curves were obtained from turbidity measurements at two widely separated wavelengths. These distributions are in agreement with distributions determined from scanning electron microscopic analysis.

Fiber-optic probe for sensitive Raman analysis

Abstract: A fiber-optic probe, useful for light scattering and luminescence measurements, which comprises at least one optical fiber for transmitting light into a sample and at least two optical fibers for collecting light from the sample. The probe may further comprise a shield surrounding the fibers and having an optical window at one end to protect the fibers from hostile environments. When used in conjunction with a laser as a light source, the probe is particularly suited for Raman spectroscopy.

The Contribution of Wedge Scattering to the Radar Cross Section of the Ocean Surface

Abstract: This letter considers the contribution to the radar cross section of the ocean surface due to scattering from edges for which the local radius of curvature is small compared with the radar wavelength. An analytic expression based on the method of equivalent currents is given for such scattering and is evaluated for several assumed sets of parameters. This contribution is shown to augment the Bragg scattering cross section in regions where the latter underestimates the measured radar cross section, while remaining smaller than the Bragg component elsewhere.

Light scattering of colloidal dispersions in non-polar solvents at finite concentrations. Silic spheres as model particles for hard-sphere interactions

Abstract: Static and dynamic light-scattering studies are reported for spherical model particles in non-polar solvents. The model particles have a core of silica and a dense surface layer of octadecylalcohol chains which makes them ‘oil soluble’. The refractive-index difference between particles and solvent is very small and so dispersions can be studied by means of light scattering up to high concentrations. Multiple-scattering effects are considered briefly. In cyclohexane the particles show repulsive forces which can be described by a hard-sphere interaction. The small refractive-index differences can also be used to detect differences in optical density in the silica core. The periphery of the core is found to be more dense than the centre. Furthermore, the small natural spread in refractive index of the particles can be used to differentiate between collective-diffusion and self-diffusion processes. Differences in refractive indexes can also be obtained by variations in the particle synthesis. In this way it is possible to study self-diffusion by following the motion of tracer particles.

Performance degradation due to stimulated Raman scattering in wavelength-division-multiplexed optical-fibre systems

Abstract: The effects of stimulated Raman scattering (SRS) on a two-channel wavelength-division-multiplexed optical-fibre communication system are analysed. For both amplitude and angle modulation the most important effect of SRS is increased loss for the short-wavelength channel, which in the worst case limits the maximum usable transmitter power to ~ 50 mW.

Temperature effects in the time‐correlator theory of resonance Raman scattering

Abstract: Within well‐defined ‘‘standard’’ assumptions and the time‐correlator theory’s separation of resonance Raman (RR) scattering into orders, previously discussed exact relations allow one to calculate mth‐order RR profile line shapes directly from optical absorption data at T≠0 K. At T=0 K, the mth‐order profiles are identical with the full m‐phonon profiles, which are the experimentally measured quantities, while for T≠0 K, the m‐phonon profiles include higher‐order corrections due to processes which freeze out at T=0 K and which involve virtual phonon excitation–deexcitation in all Franck–Condon active modes. In this paper we show that for one‐phonon scattering from a large class of multimode systems, the correction due to a thermally populated mode is small if (1) the mode’s frequency is small compared with the smallest resolvable width in the optical absorption and/or (2) the mode’s electron–phonon coupling is weak. For the multimode system β‐carotene in isopentane at T=123 and 298 K, the sum of corrections due to all thermally populated Franck–Condon active modes is found to be negligible, so that even at room temperature, the first‐order and one‐phonon profiles are essentially identical. Our first‐order profile line shapes calculated from optical absorption data for T=123 and T=298 K account well for the observed thermal broadening and are in good overall agreement with the measured one‐phonon profiles. A short‐time approximation is developed and is shown to give insight into our numerical results—in particular, in the limit of a large number of thermally populated low‐frequency modes of comparable electron–phonon coupling strengths, the sum of these modes’ higher‐order corrections to the one‐phonon profiles is shown to vanish. The negligibility of the higher‐order corrections leads to efficient T≠0 K multimode numerical modeling procedures which allow one to conveniently obtain both the optical absorption and RR profiles from a single one‐dimensional fast Fourier transform of the absorption time‐correlator. Generalizations to mth‐order scattering are briefly discussed.

Elastic and inelastic light scattering in flow cytometry.

Abstract: A review of the fundamental aspects of elastic light scattering suggests that information about the shape and internal structure may best be obtained from signals measured in the backscattering directions. Size information can be most readily extracted from forward-scattering signals. Spectral analysis of scattered signals with incident white light is a subject that merits further study. Signals from cells that have been stained with fluorescent dyes are proportional to dye content in the usual flow-cytometric configuration except in the case of dense, strongly anisometric structures such as sperm cells. The recent discovery that Raman signals from molecules adsorbed on small silver particles are strongly enhanced suggests the possibility of utilizing this effect for identification of molecular species inside biological cells.

Light-Scattering Immunoassay of Specific Proteins: A Review

Abstract: Immunoprecipitation techniques have been employed in the measurement of specific proteins for many years. The early techniques of gel precipitation are now gradually being replaced by nephelometric and turbidimetric measurement of the antigenantibody complex in free solution. The reason for this is primarily due to an increased awareness of the value of specific protein measurement combined with improvements in immunochemical reagents and advances in instrumentation. Light-scattering measurements of the antigenantibody reaction were performed as early as 1938 by Libby.' However, it was not until specific antisera became available that immunonephelometry became widely used. The work of Ritchie et al.2 using a continuous-flow system helped to identify the need of the analyst for high-affinity antibodies and a means ofenhancing the reaction rate. During the 1970s the basic work of Savory et al.3 on the kinetics of the antigen-antibody reaction paved the way for discrete nephelometric systems. At the present time a large number of commercial systems are available for immunological assays based on light scattering, including some using centrifugal analysis.s This surge of interest in immunonephelometry has stimulated a number of workers to look again at the technique of turbidimetry with the aid of polymer enhancement and high-affinity antibodies.

The application of laser light scattering to the study of biological motion

Abstract: Physical Principles of Light Scattering.- Structure and Movement in Cells.- Applications of Laser Light Scattering to Biological Systems.- Techniques and Instrumentation.- Correlation Function Profile Analysis in Laser Light Scattering I. General Review on Methods of Data Analysis.- Correlation Function Profile Analysis in Laser Light Scattering II. A Hybrid Photon Correlation Spectrometer.- Electrophoretic Light Scattering: Modern Methods and Recent Applications to Biological Membranes and Polyelectrolytes.- Laser Doppler Velocimetry in a Biological Context.- Implementation of Two Different Techniques for Measuring Lateral Diffusion and Optimisation of the Fluorescence Correlation Spectroscopy Concept.- Laser Doppler Microscopy: Especially as a Method for Studying Brownian Motion and Flow in the Sieve Tubes of Plants.- Studies of Neurotransmitter Receptor Interactions Using Quantitative Video Intensification Microscopy (V.I.M.).- Macromolecules and Gels.- Analysis of Diffusion of Biological Materials by Quasielastic Light Scattering.- The Diffusion of Compact Macromolecules Through Biological Gels.- Correlation Spectroscopy and Structural Properties of Macromolecular Solutions.- Depolarized Rayleigh Spectra of DNA in Solution.- Double Scattering in a Structured System of Particles.- Membranes and Amphiphilic Systems.- Fluorescence Techniques for the Study of Biological Motion.- Light Scattering by Model Membranes.- The Movement of Molecules Across Membranes: the Thermodynamic Analysis of the Dependence on Structure, Pressure and Temperature.- Light Scattering and Phase Transitions in GMO Membranes.- Photon Correlatior Studies of Phase Transitions in Lipid Monolayers.- Light Scattering from Micellar Solutions - Proposal for a Light Scattering Standard.- Laser Light Scattering Study of the Fractionation of Casein Micelles in Skim Milk by Controlled Pore Glass Chromotography.- Structural Studies on Bovine Casein Micelles by Laser Light Scattering.- Piological Applications.- Vesicles.- Structure and Dynamics of Disk Membrane Vesicles.- Vesicle Dynamics in Pollen Tubes.- A Preliminary Rheological Investigation of Living Physarum Endoplasm.- Muscles and Muscle Proteins.- The Application of Quasi-Elastic Light Scattering to the Study of Muscular Contraction.- Dynamic Light Scattering Study of Muscle F-Actin in Solution.- Further Evidence of Cross-Bridge Motion in Limulus Thick Myofilament Suspensions.- Stretch-Induced Transparency Change Associated With Cross-Bridge Deformation in Active Frog's Muscle.- Actin Polymerization in Cell Cytoplasm.- Ctyoplasmic Streaming.- Dynamic Cellular Phenomena in Physarum Possibly Accessible to Laser Techniques.- Amoeboid Movement in Chaoscarolinensis.- Cytoplasmic Streaming in Plant Cells and Its Relation to the Cytoskeleton.- The Rotation Model for Filament Sliding as Applied to the Cytoplasmic Streaming.- Motility.- Motility of Living Cells and Micro-organisms.- Chemotaxis and Band Formation of Escherichia coli Studied by Light Scattering.- A Comparison of Models Used in the Analysis of Quasi-Elastic Light Scattering Data from Two Motile Systems: Spermatozoa and Chlamydomonasreinhardtii.- Light Scattering Studies of Biological Populations and Biological Structures.- Systematic Assessment of Sperm Motility.- The Application of Laser Light Scattering to the Study of Photo-Responses of Unicellular Motile Algae.- Concluding Statements.- A Biologist Sums Up.- Epilogue.- Participants.

Molecular dynamics study of Rayleigh light scattering from molecular fluids

Abstract: In this article, we present the results of a molecular dynamics simulation of Rayleigh light scattering (LS) from molecular fluids. We include the orientational and collision induced (CI) contributions to the depolarized LS time correlation and the CI contribution to the isotropic LS time correlation. The intermolecular potential is represented by a two site Lennard‐Jones model. The bond length and potential parameters are chosen to correspond to those of O2 and CO2. We consider two pair polarizability models, one based on the dipole‐induced dipole (DID) interactions between molecular centers and the other on the DID interactions between Lennard‐Jones sites. For both models, we study the variations of the LS time correlations, integrated intensities, and spectral moments with density and temperature. In the case of the more anisotropic CO2, we find that the two models predict very different behavior of the CI part of the Rayleigh LS spectra. The site DID model is found to agree slightly better with the available experimental data. We discuss the implications of our results to the interpretation of Rayleigh spectra in terms of structure and dynamics of molecular fluids.