Education / Work History
Laser Induced Fluorescence Spectroscopy of Aromatic Molecules with Large-Amplitude VibrationsThe thesis is concerned with the gas phase electronic spectroscopy of selected aromatic molecules under the supersonic jet expansion environment. The molecular systems that have been chosen here posses one or more large-amplitude vibrations such as internal rotation of methyl group, N-inversion or torsional motion of hydroxyl group. The issues that we have addressed are the effects of the large-amplitude vibrations attached with the aromatic ring moiety on vibrational mode structures and dynamics in the ground (S0) and excited (S1) electronic states. Tunable narrow spectral bandwidth UV lasers have been used to excite the molecule to specific vibronic levels in the S1 state, and the excited state dynamical behavior were inferred by analyzing the dispersed fluorescence (DF) spectra measured following excitations to single vibronic levels.The work that has been performed in the thesis is briefly mentioned from chapter 1 to 7. In chapter 1, a brief review of the studies carried out on the concerned molecules using various spectroscopic methods by other research groups and the need of the studies embodied here in the backdrop of the existing knowledge emphasized. In chapter 2, the principles and technical details of experimental and theoretical methodologies to record and interpret the laser induced fluorescence excitation (FE) and DF spectra, respectively, have been described. In chapter 3, the S1↔S0 electronic spectra of aniline have been revisited to analyze the distortion of the vibrational mode characteristics in S1 state. In chapter 4, p-fluoroaniline molecule has been chosen to study the effect of fluorine atom substitution at the para position of the aniline molecule over the vibronic mode mixing phenomenon in the S1 state. Internal rotation and the N-inversion of the amine group are two large amplitude vibrations that can interact through the aromatic ring in p-methylaniline. In chapter 5, this molecule has been studied to analyze the abovementioned issue by using laser induced FE and DF spectroscopic technique. In chapter 6, with the aid of theoretical technique similar experiments have been performed to observe the effect of torsion motion of hydroxyl group on the vibronic structure in S1 state upon electronic excitation in p-fluorophenol. Methyl torsion motion generally alters the vibronic behavior of aromatic ring. In chapter 7, p-vinyltoluene molecule has been chosen to observe such effect along with the effect of extended π-conjugation on the excited state (S1) dynamics.
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