Date of Award

Summer 7-17-2014

Document Type

Thesis

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry & Biochemistry

First Advisor

David M. Jonas

Second Advisor

Steven Cundi ff

Third Advisor

Robert P. Parson

Abstract

Two-dimensional Fourier-transform (2DFT) spectra of the D2 line of rubidium vapor in argon buffer gas are simulated using a three-dimensional frequency domain solution of Maxwell's equations that treats linear propagation distortions exactly. Simulations for the homogeneous optical Bloch model at optical densities of up to 3 are compared to measured rephasing 2DFT spectra. Experimentally observed propagation distortions are qualitatively reproduced in calculated 2DFT spectra, including peak broadening, peak splitting, and peak twisting. Varying beam overlap through the sample is crudely modeled in simulations, demonstrating that reduced beam overlap causes narrowing of the peak shape in the excitation dimension and an overall reduction in signal size. Propagation distortions, including peak splitting depth and peak twist, are found to vary with waiting time and with the excited state lifetime at a fixed total dephasing time, suggesting a coherent mechanism.

A new method for reducing repetitive excitation of the sample by scanning beams with respect to a stationary sample cell using a fast steering mirror is described. This apparatus extends the average time between excitations at any point in the sample to >0.3 s and accommodates a wide variety of sample cell formats, including cryostats, air-tight cuvettes, and flow cells.

Colloidal indium arsenide (InAs) quantum dots (QDs) are interrogated by degenerate pump{ probe transient absorption spectroscopy at a photon energy of approximately 1.5 times the band gap using spatially-averaged excitation probabilities lower than in previously reported studies. Signatures of Auger recombination appear with a timescale of 26 +/- 5 ps. Carrier cooling and recombination pathways are explored, revealing new dynamics not observed in studies that probe the band edge.

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