Intramolecular vibrational energy redistribution (IVR) in selected S1 levels above 1000 cm−1 in para-fluorotoluene

Whalley, Laura E.

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https://hdl.handle.net/2142/96814 Copy

Description

Title

Intramolecular vibrational energy redistribution (IVR) in selected S1 levels above 1000 cm−1 in para-fluorotoluene

Author(s)

Whalley, Laura E.

Contributor(s)

• Wright, Timothy G.
• Reid, Katharine L.
• Davies, Julia A.
• Tuttle, William Duncan
• Gardner, Adrian M.

Issue Date

2017-06-23

Keyword(s)

Vibrational structure/frequencies

Abstract

With increasing vibrational wavenumber, the density of states of a molecule is expected to rise dramatically, especially so when low wavenumber torsions (internal rotations) are present, as in the case of textit{para}-fluorotoluene (textit{p}FT). This in turn is expected to lead to more opportunities for coupling between vibrational modes, which is the driving force for intramolecular vibrational energy redistribution (IVR). Previous studiesfootnote{C. J. Hammond, V. L. Ayles, D. E. Bergeron, K. L. Reid and T. G. Wright, textit{J. Chem. Phys.}, textbf{125}, 124308 (2006)}$^{,}$footnote{J. A. Davies, A. M. Green, A. M. Gardner, C. D. Withers, T. G. Wright and K. L. Reid, textit{Phys. Chem. Chem. Phys.}, textbf{16}, 430 (2014)} at higher energies have focussed on the two close lying vibrational levels at ~1200 cm$^{-1}$ in the S$_{1}$ electronic state of textit{p}FT which were assigned to two zero-order bright states (ZOBSs), whose characters predominantly involve C-CH$_{3}$ and C-F stretching modes. A surprising result of these studies was that the photoelectron spectra showed evidence that IVR is more extensive following excitation of the C-F mode than it is following excitation of the C-CH$_{3}$ mode, despite these levels being separated by only 35 cm$^{-1}$. This observation provides evidence that the IVR dynamics are mode-specific, which in turn may be a consequence of the IVR route being dependent on couplings to nearby states that are only available to the C-F mode. _x000d_ _x000d_ In this work, in order to further investigate this behaviour, we have employed resonance-enhanced multiphoton ionisation (REMPI) spectroscopy and zero-kinetic-energy (ZEKE) spectroscopy to probe S$_{1}$ levels above 1000 cm$^{-1}$ in textit{p}FT. Such ZEKE spectra have been recorded via a number of S$_{1}$ intermediate levels allowing the character and coupling between vibrations to be unravelled; the consequence of this coupling will be discussed with a view to understanding any IVR dynamics seen.

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

text

Language

eng

Permalink

http://hdl.handle.net/2142/96814

DOI

https://doi.org/10.15278/isms.2017.FC05

Copyright and License Information

Copyright 2017 Laura E. Whalley

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