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The electron density in a plasma jet has been determined as a function of position in the jet by measurements of the coherent scattering of laser light. The electron density profiles thus obtained are compared with profiles obtained from measurements of spectral line intensities. The results of these two diagnostic methods are seen to agree within experimental error. For the experiment described here, the scattering is from correlated motion of the electrons, and the scattered light spectrum has distinct electron satellites. It is shown that the width of these satellites, observed in earlier work by Chan and Nodwell (1966), may be accounted for by the electron density gradients in the plasma. This thesis gives a short review of techniques and relevant theory, with emphasis on experimental problems. A brief discussion of perturbation of the plasma by the laser light is also included. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

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Tissue, in particular its mechanical properties, is of interest from a material science point of view. The collagen fiber framework found in nearly all tissue forms the basis for the tissue's behavior. Connective tissue provides more interesting behavior, designed to bear significant load in one direction, while retaining the ability to stretch in other directions. Contributing factors to such behavior are fiber diameter and orientation. Small angle scattering analysis has been developed over the past century. Particular attention has been paid to x-ray and neutron scattering, both of which characterize features on a nanometer scale. Small angle light scattering (SALS) has the ability to characterize features on a micron scale, and is thus suitable for the analysis of collage fibers. Scattering data from several tendons were analyzed using the Generalized Indirect Fourier Transform (GIFT) program developed by Dr. Otto Glatter. The data is fit using cubic B-splines, and transformed into a probability density distribution function (abbreviated PDDF or p(r)). The PDDF can then be interpreted to give an average fiber diameter, as well as other structural information. Since this type of analysis has never been performed on collagen fibers, emphasis was placed on validating small angle light scattering as an appropriate technique to characterize collagen fiber diameter. This was accomplished by comparing the results with optical microscopy. Results from SALS analysis agree with features observed by optical microscopy. Small angle light scattering analysis is able to provide an analysis of structures superior to that of optical microscopy. Small angle scatter theory provides a three dimensional analysis of the structure. On the other hand, optical microscopy provides only a two dimensional view of the sample. The structure of collagen fibers in tissue is certainly three dimensional, making small angle light scattering a more suitable technique for characterization.

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The design, construction and details of operation of an instrument for measuring Bidirectional Scattering Distribution Functions (BSDF) {i.e., Bidirectional Reflection Distribution Functions (BRDF) and Bidirectional Transmission Distribution Functions (BTDF)} at four wavelengths from the visible to the far infrared (FIR) are presented. Hardware, software, theory, calibration, accuracy and performance are all addressed. The four major interacting subsystems--optical, electronic, mechanical and computer--are discussed in various degrees of detail. A BASIC language control program for running the system via the Z-80 microprocessor is included in the appendix. The origin of BRDF is traced, and a brief theoretical summary examines it from both a physical optics and a radiometric point of view. Modeling is performed to determine the effect of large radiometer collecting apertures on accuracy. Dynamic range and resolution are determined from experimental and theoretical considerations. Finally, new measurements of Martin Black at 118.8 (mu)m are presented along with measurements at 0.6328, 3.39 and 10.6 (mu)m. The FIR BRDF measurements covered 6 orders of magnitude and values as low as 6 x 10('-4) sr('-1) have been recorded.

Population pulsations are fluctuations in the population difference (of a two level system) due to the presence of two or more coherent waves interfering in the medium. In this work, we show that population pulsations generated by three waves, a central wave and two mode-locked sidebands, are responsible for both the multiwavelength and the single-wavelength instabilities of single-mode lasers containing homogeneously-broadened media. The role of the population pulsations in establishing these instabilities, however, diminish as the central mode is detuned away from the atomic resonance frequency. For homogeneously-broadened lasers, we find two regions of single-wavelength instability. The first is at line center, for which population pulsations are solely responsible, and the second is off line center where the unsaturated medium provides the required gain and anomalous dispersion. For the case of inhomogeneously-broadened lasers, we show that population pulsations significantly increase the instability range over that predicted by Casperson for single-mode bad-cavity lasers. Both the unidirectional ring and the standing-wave cavities are treated. The Fourier expansion technique, used in this work, for treating three-frequency operation in saturation spectroscopy is shown to be equivalent (in appropriate limits) to the linear stability analysis in laser theory and optical bistability. We also show, in single-sideband saturation spectroscopy, that for long interaction lengths propagation effects can significantly influence the absorption and dispersion coefficients of the medium. Finally, we show that under certain conditions the pronounced splittind effects of the population pulsations develop into regions of intense absorption.

The scattered radiation fields in spherical planetary atmospheres have been considered by a new method which is called the Quasi-Spherical method. This method is applicable to planets with radii which are much larger than the height of their atmosheres. The scattering of 0.5 (mu)m radiation in a conservative and vertically inhomogeneous atmosphere has been discussed. Results comparing the emerging radiation from plane-parallel and spherical models for the earth's atmosphere have been presented for four different aerosol distributions in addition to the normal molecular composition. These results indicate measurable differences on the order of 10 to 300% as the angle of observation and/or the angle of incident sun falls within 10(DEGREES) from the horizon. Also, the obtained results in the spherical atmosphere show that additional layers of aerosols in either the stratosphere or the troposphere can be detected by satellite or aircraft radiometric measurements, while the plane-parallel atmosphere does not permit such a detection. The accuracy of the obtained results by the present method can be increased by increasing the number of spherical shells in the spherical atmosphere. The emerging radiation in homogeneous and inhomogeneous Rayleigh atmospheres as computed by the Quasi-Spherical and the Monte Carlo methods compare quite well. By applying the divergence theorem it was shown by the present method that the total flux in the spherical atmosphere is conserved within 1.351%.

A system consisting of a sphere sitting on a clean mirror was modeled as a two particle system: the real sphere and its image sphere, treating the mirror as a conducting plane. When the system was irradiated with a plane-polarized collimated laser beam with varying angles of incidence, the scattering from each particle was assumed to follow Mie's solution for light scattering by a sphere. Phase difference between the scattering by the real sphere and the one by its image sphere was assessed by the geometry of the model. The far field solutions from each of the spheres were added to yield a phase dependent intensity function. Another model assumed no phase correlation between the two and the intensities from each spheres were added. Also discussed is the Double Interaction Mode, which takes the mirror-sphere separation into consideration. These theoretical results were converted to Bidirectional Reflectance Distribution Functions (BRDF). The theoretical as well as the empirical surface scattering from a good quality optical surface was introduced. The BRDF values thus calculated were added to the background scattering by the mirror since no interaction was assumed between the spheres and the rough metallic surface of the mirror. The test sample was prepared with polystyrene spheres with the nominal diameter of 0.984 μm on a high quality aluminum mirror. The BRDF data from this sample with 6328Å and 4416Å were compared with the one obtained with the model described above. The comparison strongly indicated that there existed no phase correlation between the scatterings by the two spheres. Determination of the sphere size and practical applicability for estimating the sphere number density on the surface are also discussed.