Resonance Hyper-Raman Characterization of Nonlinear Chromophores

Hyper-Raman spectroscopy is a nonlinear optical probe which can be used to explore the multi-photon properties of molecules. Three studies are presented in this dissertation. The first study is a combined experimental investigation of the surfaceenhanced hyper-Raman scattering with a theoretical study of the electronic states of the Rhodamine 6G molecule. This study demonstrates that hyper-Raman spectroscopy can be used to probe electronic states which are one-photon inaccessible. The second study involves a comparison of experimentally measured resonance hyper-Raman spectra to first-principles calculations of the resonance hyper-Raman scattering. This study shows the utility of coupling hyper-Raman spectroscopy and hyper-Raman calculations to define the multi-photon properties of the molecule. The final study compares the experimentally collected surface-enhanced hyper-Raman spectra of Rhodamine 6G to the theoretical simulations of the resonance hyper-Raman for identical excitation energies. In this study, the mechanism of vibronic coupling in the hyper-Raman effect is fully explained, demonstrating the capability of hyper-Raman spectroscopy predicting the two-photon absorption mechanism.