High Resolution Laser Spectroscopy of Supersonic Jet-Cooled Molecules

Citation

Keelan, Brian William (1986) High Resolution Laser Spectroscopy of Supersonic Jet-Cooled Molecules. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/n788-xq67. https://resolver.caltech.edu/CaltechETD:etd-04032008-111202

Abstract

The phenomenon of intramolecular vibrational redistribution (IVR) is currently of significant theoretical and practical interest. Consideration of a simple model raises several important questions about the coupling mechanisms responsible for NR. A review of recent work indicates that these questions are best addressed using complimentary high resolution spectral and temporal experiments, as have been reported elsewhere for only two large molecules. Thus, a tunable laser - free jet apparatus capable of producing fluorescence excitation, dispersed fluorescence, and rotational band contour spectra was constructed and is described in detail herein. High resolution spectral. data obtained using this apparatus is presented for five molecules for which complimentary temporal data is now available: stilbene, diphenylbutadiene, anthracene—h₁₀, anthracene-9d₁, and anthracene—d₁₀. Analysis of the spectral data yields information about coupling mechanisms which is relevant to the questions proposed initially.

The results obtained support the following conclusions for these molecules: (1) anharmonic coupling predominates at ranges of ≈ 1 - 10 cm^-1, but Coriolis coupling may also be important at shorter ranges; (2) molecular symmetry influences coupling by limiting the number of nearby levels with which a given level may interact; and (3) coupling is more extensive at higher vibrational densities of states due .to the increased number of levels of the appropriate symmetry lying within the effective coupling range of a given level.

Thesis Files