Thesis Abstract
Laser Induced Fluorescence Spectroscopy of Selected Organic Molecules in Supersonic Jet Expansion
The thesis is concerned with the gas phase electronic spectroscopy of selected
aromaticmolecules under the supersonic jet expansion environment. The main
issues addressed in thework embodied in this thesis are conformational analysis
and vibrational mode mixing in fewselected organic molecules. Fluorescence
excitation and dispersed fluorescence spectroscopytechniques have been employed
with the help of tunable narrow spectral bandwidth UVlasers. Computational ab
inito and DFT (density functional theory) methods have beenextensively employed
to support the experimental observation. In chapter K the theoretical principles
underlying laser induced fluorescence, supersonicjet expansion and computational
chemistry are detailed followed with a brief descriptionabout the methodology of
the experiment and computation in the second chapter.Conformation of phenetole
2(p-fluorophenyl)ethanoi have been determined where theformer is shown to exist
in a single conformer in the jet and three conformers of the latterare observed
in the jet. Using computational methods, these-observations are corroboratedand
details of these are given in parts A and B of chapter 3. In the same
chapter,conformation of ephedrine and fluorescence studies of tryptamine and
tryptophan are also detailed, fluorescence results show no difference from the
earlier reports which pertainedto ionization spectroscopy methods. These details
are given in parts C and D of chapter 3.S1↔S0 electronic spectroscopy of
1-methoxynaphthalene, styrene and p-fluorostyrene(4FS) show extensive mode
mixing characteristics which are detailed in chapters 4 and 5.The out-of-plane
vibration of the vinyl group in styrene and 4FS get extensively mixedwith
several other ring vibration modes upon electronic excitation to the S1
electronic state.
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