Graduation Year

2005

Document Type

Dissertation

Degree

Ph.D.

Degree Granting Department

Electrical Engineering

Major Professor

Arthur David Snider, Ph.D.

Committee Member

Wilfrido Moreno, Ph.D.

Committee Member

Kenneth Buckle, Ph.D.

Committee Member

Stanley Deans, Ph.D.

Committee Member

Oscar D. Crisalle, Ph.D.

Keywords

Particle analysis, Spherical particles, Non-spherical particles, In suspension particles, Rayleigh-debye-gans

Abstract

The area of particle characterization is expansive; it contains many technologies and methods of analysis. Light spectroscopy techniques yield information on the joint property distribution of particles, comprising the chemical composition, size, shape, and orientation of the particles. The objective of this dissertation is to develop a hybrid scattering-absorption model incorporating Mie and Rayleigh-Debye-Gans theory to characterize submicron particles in suspension with multiwavelength spectroscopy.

Rayleigh-Debye-Gans theory (RDG) was chosen as a model to relate the particles joint property distribution to the light scattering and absorption phenomena for submicron particles. A correction model to instrument parameters of relevance was implemented to Rayleigh-Debye-Gans theory for spheres. Behavior of nonspherical particles using RDG theory was compared with Mie theory (as a reference). A multiwavelength assessment of Rayleigh-Debye-Gans theory for spheres was conducted where strict adherence to the limits could not be followed. Reported corrections to the refractive indices were implemented to RDG to try and achieve Mies spectral prediction for spheres.

The results of studies conducted for RDG concluded the following. The angle of acceptance plays an important role in being able to assess and interpret spectral differences. Multiwavelength transmission spectra contains qualitative information on shape and orientation of non-spherical particles, and it should be possible to extract this information from carefully measured spectra. There is disagreement between Rayleigh-Debye-Gans and Mie theory for transmission simulations with spherical scatterers of different sizes and refractive indices.

A hybrid model combining RDG and Mie theories was developed and tested for spheres of different sizes and refractive indices. The results of hybrid model is that it approximates Mie theory much better than Rayleigh-Debye-Gans for particle sizes smaller than the wavelength and for a broader range of optical properties in the context of multiwavelength spectroscopy. Overall, this new model is an improvement over Rayleigh-Debye-Gans theory in approximating Mie theory for submicron particles and is computationally more effective over other methods. The development of the hybrid spherical model constitutes a platform for developing nonspherical models

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