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 Title: High pressure light scattering studies of molecular dynamics in dense fluids Author(s): Song, Xiaomin Doctoral Committee Chair(s): Jones, J. Department / Program: Chemistry, AnalyticalChemistry, Physical Discipline: Chemistry, AnalyticalChemistry, Physical Degree Granting Institution: University of Illinois at Urbana-Champaign Degree: Ph.D. Genre: Dissertation Subject(s): Chemistry, Analytical Chemistry, Physical Abstract: This thesis deals with high pressure light scattering studies of the vibrational relaxation of N$\sb2$O, the intermolecular interactions in naphthalene and CO$\sb2$ supercritical fluid, the collision induced scattering in rotational spectra of several linear molecules, and the pure collision induced spectra of CO$\sb2$ in CO$\sb2$-Ar, CO$\sb2$-Xe, CO$\sb2$-CO and CO$\sb2$-N$\sb2$ systems. A better understanding of the molecular dynamics in dense fluids represents the main aim of this work.In the study of vibrational spectra of N$\sb2$O, we investigated the band widths and the frequency shifts of $\nu\sb1$ and $\nu\sb3$ Raman bands of N$\sb2$O at different temperatures and pressures. Different theoretical models including direct dephasing and indirect dephasing and the vibrational energy transfer were tested. This study shows that the vibrational energy transfer dominates the vibrational relaxation process of N$\sb2$O.The intermolecular interactions in naphthalene and CO$\sb2$ are studied by means of the Raman spectra from naphthalene and CO$\sb2$. The $\nu\sb1$, $\nu\sb8$ and $\nu\sb9$ bands of naphthalene show a blue shift while the Fermi resonance symmetric stretching mode of CO$\sb2$ shows a red shift with increasing density. These experimental results suggest that the interactions between molecules in this system should be modeled as site-to-site interactions. While the overall interaction between naphthalene and CO$\sb2$ is attractive, some of the naphthalene bonds may feel repulsive force. The electrostatic quadrupole-quadrupole interaction model effectively explained the association energy and the frequency shifts of the band.The collision induced effects are studied for linear molecules N$\sb2$O, O$\sb2$, N$\sb2$ and CO$\sb2$. By analyzing the line shapes, the intensities, the second and the fourth moments of the depolarized Rayleigh and Raman spectra from these linear molecules, we discussed the relationship of the collision induced effects to the rotational spectra. The Raman forbidden spectrum of CO$\sb2$ is studied in CO$\sb2$-Ar, CO$\sb2$-Xe, CO$\sb2$-CO and CO$\sb2$-N$\sb2$ mixtures. The intensities and the band widths of the $\nu\sb2$ forbidden band of CO$\sb2$ measured in the different mixtures are compared and the results indicate that the quadrupole-dipole interaction process (A$\alpha$) is responsible for the Raman forbidden spectrum. Issue Date: 1989 Type: Text Language: English URI: http://hdl.handle.net/2142/23679 Rights Information: Copyright 1989 Song, Xiaomin Date Available in IDEALS: 2011-05-07 Identifier in Online Catalog: AAI8916310 OCLC Identifier: (UMI)AAI8916310
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