Electronic and photoelectron spectroscopy of substituted benzene molecules

Tuttle, William Duncan (2018) Electronic and photoelectron spectroscopy of substituted benzene molecules. PhD thesis, University of Nottingham.

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Intramolecular vibrational redistribution (IVR) has long been investigated in para-fluorotoluene (pFT), with many comparisons made to para-difluorobenzene (pDFB). These comparisons have shown an increased IVR rate for pFT compared to pDFB at similar internal energies, and there are two factors which could influence this – the addition of the methyl group and the lowering of the symmetry of the molecule. This thesis looks to separate these two effects by introducing a comparison of pFT to para-chlorofluorobenzene, as well as an additional comparison of para-xylene (pXyl) to pDFB.

Resonance-enhanced multiphoton ionisation (REMPI) spectra of these four molecules are presented, with zero-electron-kinetic-energy (ZEKE) photoelectron spectra recorded via many intermediate levels up to ~00+1200 cm-1 for both pFT and pXyl. These ZEKE spectra allow the assignment of many torsional, vibrational and vibration-torsion levels in these two molecules, with pXyl treated with the appropriate G72 molecular symmetry group for the first time. Several reassignments, as well as many new assignments, are presented for pFT and pXyl.

Use of the REMPI and ZEKE techniques allows for the probing of any couplings between levels in the S1 state, as well as providing ground state cation information, and this is supplemented by comparison of REMPI activity between the four para-disubstituted benzene molecules. Proposed couplings, which appear to become more widespread at higher internal energies, are supported by density of states calculations, and a discussion of the influence of both the methyl group and the molecular symmetry on the couplings is presented.

Item Type: Thesis (University of Nottingham only) (PhD)
Supervisors: Wright, Timothy G.
Keywords: Benzene molecules; Benzene spectra
Subjects: Q Science > QD Chemistry > QD241 Organic chemistry
Faculties/Schools: UK Campuses > Faculty of Science > School of Chemistry
Item ID: 54244
Depositing User: Tuttle, William
Date Deposited: 23 Jan 2019 15:40
Last Modified: 11 Dec 2020 04:30
URI: https://eprints.nottingham.ac.uk/id/eprint/54244

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