Spectroscopic and theoretical investigation of selected cyclic and bicyclic molecules in their ground and excited electronic states

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Title: Spectroscopic and theoretical investigation of selected cyclic and bicyclic molecules in their ground and excited electronic states
Author: Rishard, Mohamed Zuhair Mohamed
Abstract: The structures , vibrational frequencies , and potential energy functions of several molecules in their ground and excited electronic states were determined using various spectroscopic and theoretical methods . High -level ab initio and density functional theory (DFT ) calculations were utilized to investigate the previously reported structures and vibrational spectra of 1 ,3 - disilacyclobutane (13DSCB ) and its 1 ,1 ,3 ,3 -d4 (13DSCB -d4 ) isotopomer . These calculations confirmed the finding from earlier microwave work that the CSiC angles of the 13DSCB ring are unexpectedly larger than the SiCSi angles . The calculated vibrational spectra using density functional theory agreed well with the experimental data and showed CH2 modes to have unusually low values . The calculations also confirmed that the individual molecules in the vapor phase are puckered whereas in the solid they become planar . The one -dimensional potential energy surfaces (PESs ) for the ring inversion vibration of 2 -cyclohexen -1 -one and its 2 ,6 ,6 -d3 isotopomer in its ground and singlet S1 (n , ?* ) electronic states were determined using ultraviolet cavity ringdown spectroscopy (CRDS ) . The CRDS data allowed several of the quantum states of the ring inversion vibration to be determined for both the ground and excited electronic states , and the data were fit very well with PESs with high barriers to inversion . The infrared and Raman spectra and DFT calculations were utilized to complete a vibrational assignment of 2CHO and 2CHO -d3 . A remarkable agreement was seen between the experimental and calculated spectra . The fluorescence excitation spectra (FES ) and the single -vibronic level fluorescence (SVLF ) spectra of jet -cooled 1 ,4 -dihydronaphthalene (14DHN ) were acquired to determine its ring -puckering potential energy function for the ground and singlet S1 ( ? , ?* ) electronic states . Ultraviolet , infrared , and Raman spectra were also recorded to complement the analysis . The potential energy functions showed that the molecule is planar in both the ground and S1 ( ? , ?* ) states . A complete vibrational assignment was carried out for 14DHN using the infrared and Raman data and aided by DFT calculations . The ab intio calculations carried out on 2 -methyl -2 -cyclopenten -1 -one (2MCP ) showed that the molecule can have 3 different conformers . Infrared and Raman spectra of the liquid -phase molecule were recorded and analyzed to complement the theoretical calculations .
URI: http : / /hdl .handle .net /1969 .1 /ETD -TAMU -2030
Date: 2009-05-15

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Spectroscopic and theoretical investigation of selected cyclic and bicyclic molecules in their ground and excited electronic states. Available electronically from http : / /hdl .handle .net /1969 .1 /ETD -TAMU -2030 .

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