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UBC Theses and Dissertations

The interaction of visible and infrared radiation with molecular and metallic particles Preston, Thomas Colin


In this thesis, the electromagnetic spectra of both conducting and non-conducting particles are studied. The relationship between particle shape and spectra is explored through both modeling and experiments. Depending on the situation, spectra are modeled using techniques such as the discrete dipole approximation, the vibrational exciton model, various electrostatic methods, or density functional theory. These results are used to not only characterize the particles in the system of interest, but also understand how particle architecture influences its spectrum. Furthermore, it is demonstrated how the consideration of a particle's symmetry, and when appropriate the symmetry of the crystal structure that forms a particle, can greatly simplify the interpretation of spectra. The main systems studied in this work are Au nanoparticles and molecular aerosol particles composed of either pure C₂H₂, pure CO₂, mixtures of pure C₂H₂ and pure CO₂ or co-crystalline CO₂·C₂H₂. The molecular aerosol particles that are studied here were chosen due to their relevance to many planetary atmospheres. Several questions concerning the phase and shape of these molecular particles are addressed and answered. Finally, the similarities between the electromagnetic response of conducting and non-conducting particles are discussed at several points in this thesis. Hybridization schemes are shown to be a powerful tool for understanding the spectra of complex nanostructures. These schemes involve decomposing complex structures into primitive components. Spectra can then be understood as mixtures of the spectra of these primitive components. For the first time a formalism is developed that allows for such hybridization methods to be extended to non-conducting particles.

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