Adrian M. Gardner, Alistair M. Green, Victor M. Tamé-Reyes, Victoria H. K Wilton and Timothy G. Wright Electronic and Photoelectron Spectroscopy of Toluene 67 th International Symposium on Molecular Spectroscopy Ohio State University 19 th June 2012

Introduction: Vibrational Modes Often, vibrations are considered in the harmonic approximation. Within this approximation normal vibrational modes are considered to be independent. However, true vibrational eigenstates are a linear combination of the harmonic levels.

Introduction: Aims Many vibrational levels in the S 1 electronic state of toluene- h 8 have been assigned by Hickman et al. 1 This was achieved by recording dispersed fluorescence spectra via many of the observed S 1 vibrational levels. In the present investigation we aim to gain information on the toluene cation by employing 1+1 ′ Zero Kinetic Energy (ZEKE) photoelectron spectroscopy. We also study the toluene- d 3 isotopologue in order to investigate the effects of the small isotopic shifts of vibrational frequencies on the appearance of electronic and photoelectron spectra of like molecules. 1.C. G. Hickman, J. R. Gascooke and W. D. Lawrance, J. Chem. Phys., 104, 4887 (1995).

REMPI Spectra Toluene- h 8 Toluene- d 3 Qualitatively, the two spectra are very similar. An intense feature, assigned to the M 29 1 vibration, dominates this wavenumber range. The relatively weak S 1 origin band is an effect of low UV intensity.

Toluene-h 8 Toluene-d 3 ZEKE Spectra via a Fermi Resonance Hickman et al. 1 previously assigned the bands labelled B and C as a Fermi Resonance between the M 11 1 and M 19 1 M 20 1 vibrations. Davies et al. 2 later proved the presence of a third coupled vibration in this Fermi Resonance, assigned M 14 2 in the present nomenclature. x2 + 1.C. G. Hickman, J. R. Gascooke and W. D. Lawrance, J. Chem. Phys., 104, 4887 (1995). 2. J. A. Davies, A. M Green and K. L. Reid, PCCP, 12, 9872 (2010).

Toluene-h 8 Toluene-d 3 ZEKE Spectra via a Fermi Resonance

Toluene-h 8 Toluene-d 3 ZEKE Spectra via a Fermi Resonance

Toluene-h 8 Toluene-d 3 ZEKE Spectra via a Fermi Resonance

Toluene-h 8 Toluene-d 3 ZEKE Spectra via a Fermi Resonance

Toluene-h 8 Toluene-d 3 ZEKE Spectra via a Fermi Resonance

Intramolcular Vibrational Energy Redistribution Hickman et al. 1 assigned the two bands, denoted I and J, as a Fermi Resonance between the M 18 1 M 19 1 and M 10 1 vibrations.

Intramolcular Vibrational Energy Redistribution Hickman et al. 1 assigned the two vibrations, denoted I and J, as a Fermi Resonance between the M 18 1 M 19 1 and M 10 1 vibrations. The ZEKE spectra recorded via these two levels show a broad, noisy “hump”, a signature of IVR. Similar observations are made in the DF recorded via these intermediate levels. 1. C. G. Hickman, J. R. Gascooke and W. D. Lawrance, J. Chem. Phys., 104, 4887 (1995).

Intramolecular Vibrational Energy Redistribution 1. C. G. Hickman, J. R. Gascooke and W. D. Lawrance, J. Chem. Phys., 104, 4887 (1995). 3. G. Varsányi, Assignments of the Vibrational Spectra of Seven Hundred Benzene Derivatives, (Wiley, New aaaaYork, 1974) Vol. 2. Varsányi 3 mode 1 Hickman et al. 1 assigned the two vibrations, denoted I and J, as a Fermi Resonance between the M 18 1 M 19 1 and M 10 1 vibrations. The ZEKE spectra recorded via these two levels show a broad, noisy “hump”, a signature of IVR. Similar observations are made in the DF recorded via these intermediate levels.

Intramolecular Vibrational Energy Redistribution Similarly, the dispersed fluorescence spectra, 1 and ZEKE spectra recorded via L show a broad, noisy “hump”. This intermediate level was assigned to the M 6 1 vibration by observation of this band in the DF spectrum– also observed in the ZEKE spectrum. As in the M 10 1 vibration, this mode contains significant C-CH 3 stretching character – a possible mechanism for the acceleration of IVR? 1.C. G. Hickman, J. R. Gascooke and W. D. Lawrance, J. Chem. Phys., 104, 4887 (1995).

Conclusions REMPI and ZEKE spectra recorded for toluene- h 8 and toluene- d 3 have been presented. The spectra for each isotopologue are qualitatively very similar; however the small shifts in vibrational frequency upon deuteration result in changes in the appearance of the spectra. Evidence for IVR has been observed in spectra recorded via low frequency S 1 intermediate levels. In these instances, the vibrational modes involve contain significant stretching C-CH 3 motion.

Professor Timothy Wright Dr Alistair Green Victor Tamé-Reyes Victoria Wilton Professor Katharine Reid Dr Julia Davies Acknowledgements

Experimental Apparatus