Investigations of temperature and pressure effects on the behavior of solvent-solute interactions via Raman spectroscopic technique

Min-Hom Aron Hu, Purdue University

Abstract

This thesis represents an effort to resolve the solvent effects by using versatile Raman spectroscopic techniques combined with available molecular models. In the pressure variation study of the Fermi resonance, the associated change of the Fermi coupling constant, W, was determined using the relative intensity, R, and the frequency splitting, δ, of the Fermi doublet measured at different pressures. In spite of a significant experimental uncertainty, a global standard perturbation analysis of the experimental R and clearly illustrates the utility of this pressure dependent method. The study of isomerization reactions as a function of temperature and pressure is another example used to demonstrate the significant effects of solute-solvent interactions on chemical equilibria. The general findings of this study indicate that the isomerization enthalpy, ΔH, and volume, ΔV, induced by both temperature and pressure are consistent with the predictions of the semi-empirical Perturbed Hard Fluid (PHF) treatment, which uses the Excluded Volume Anisotropy (EVA) model and van der Waals mean field approximation to estimate the mean intermolecular repulsive and attractive contributions of solvation energy changes. Finally, the idea of the frequency difference of Raman Stokes/anti-Stokes shifts, which originally comes from the intriguing theoretical predictions of Buckingham in the early 1960's, was verified experimentally. To achieve the required accuracy in frequency measurements, a newly designed single-fiber Raman microscopic instrument was introduced as well.

Degree

Ph.D.

Advisors

Ben-Amotz, Purdue University.

Subject Area

Chemistry

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