Direct observation of vibrational energy dispersal <i>via</i> methyl torsions

Gardner, Adrian M.; Tuttle, William D.; Whalley, Laura E.; Wright, Timothy G.

doi:10.1039/c7sc05309f

Cited by 26 publications

(53 citation statements)

References 58 publications

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“…In recent work from our group, we have focused on the study of vibrations of substituted benzenes in the S1 state and cation, with a particular interest in identifying common activity across related molecular species. We have recorded resonance-enhanced multiphoton ionization (REMPI) spectra of the three lightest monohalobenzenes, 1,2,3 toluene 4,5 , parafluorotoluene (pFT) 6,7,8 and para-xylene (pXyl) 9,10 . The establishment of common activity across a series of molecules requires the use of a consistent labelling scheme, which we have noted is required to be different for monosubstituted benzenes, 11 ortho-12 meta- 13 and the paradisubstituted benzenes.…”

Section: Introductionmentioning

confidence: 99%

Vibrations of the p-chlorofluorobenzene cation

Kemp

Whalley

Tuttle

et al. 2018

Phys. Chem. Chem. Phys.

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The vibrations of the ground state cation (X[combining tilde]2B1) of para-chlorofluorobenzene (pClFB) have been investigated using zero-electron-kinetic-energy (ZEKE) spectroscopy. ZEKE spectra were recorded using different vibrational levels of the S1 state as intermediate levels, for which assignments were put forward in an earlier paper [W. D. Tuttle, A. M. Gardner, and T. G. Wright, Chem. Phys. Lett., 2017, 684, 339]. These different intermediate levels dramatically modify the Franck-Condon factors for the ionization step. The adiabatic ionization energy (AIE) for pClFB was measured as 72 919 ± 5 cm-1, and analysis of the vibrational structure in the ZEKE spectra allowed further interrogation of the assignments of the REMPI spectrum. Assignment of the vibrational structure has been achieved by comparison with corresponding spectra of related molecules, via quantum chemical calculations, and via shifts in bands between the spectra of the 35Cl and 37Cl isotopologues. In this way it was possible to assign twenty out of the thirty vibrational modes of the ground state pClFB+ cation. Additionally, evidence for Fermi resonances between some vibrational levels was found in the S1 state, but no large-scale intramolecular vibrational redistribution (IVR) was seen in the spectra here. Finally, we discuss trends in AIE shifts for benzenes with one or two halogen atoms or methyl substituents.

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Section: Introductionmentioning

confidence: 99%

Vibrations of the p-chlorofluorobenzene cation

Kemp

Whalley

Tuttle

et al. 2018

Phys. Chem. Chem. Phys.

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“…The 2D-LIF apparatus has been described recently. 29 The vapour above room temperature parafluorotoluene (99% purity, Alfa Aesar) was seeded in~5 bar of Ar and the gaseous mixture passed through a General Valve pulsed nozzle (750 μm, 10 Hz, opening time of 180-210 μs) to create a free jet expansion. This was intersected at X/D~20 by the frequency-doubled output of a single dye laser, operating with C540A.…”

Section: Methodsmentioning

confidence: 99%

“…16 Earlier work includes: absorption studies by Cvitaš and Hollas 17 and Seliskar et al; 18 LIF and dispersed fluorescence (DF) spectroscopy by Okuyama et al, 19 Ha et al 20 and Parmenter, Zhao et al; 21,22,23,24 and resonanceenhanced multiphoton ionisation (REMPI) spectroscopy by Georgiev et al 25 and Hu et al 26 , in both cases as part of a study of the pFT-Ar complex. Further work on higher-lying S1 levels has been undertaken using tr-PES, 27 ZEKE 28,29 and 2D-LIF spectroscopy. 29 (A reassignment of the levels discussed in Ref.…”

Section: Introductionmentioning

confidence: 99%

“…Further work on higher-lying S1 levels has been undertaken using tr-PES, 27 ZEKE 28,29 and 2D-LIF spectroscopy. 29 (A reassignment of the levels discussed in Ref. 27 has been presented in Ref.…”

Section: Introductionmentioning

confidence: 99%

“…Overall, these vibtor interactions provide increased pathways for energy dissipation between the molecular motions and so can lead to the possibility of rapid intramolecular vibrational redistribution (IVR) at even quite low wavenumbers, and this has been compared and contrasted in recent papers focused on toluene, p-difluorobenzene (pDFB) and pFT, 6 as well as pDFB, p-chlorofluorobenzene (pClFB), pFT and pXyl. 33 Recently, 29 we showed that the vibtor levels at~845 cm -1 associated with the methyl torsion and the first overtone of an out-of-plane vibration in pFT were opening up new routes to interactions involving vibrations of different symmetry. This involved interactions between an excited torsional level of an overtone with vibtor levels formed by combinations with a set of levels at~400 cm -1 .…”

Section: Introductionmentioning

confidence: 99%

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Unravelling overlaps and torsion-facilitated coupling using two-dimensional laser-induced fluorescence

et al. 2018

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Two-dimensional laser-induced fluorescence (2D-LIF) spectroscopy is employed to identify contributions to fluorescence excitation spectra that arise from both overlapping bands and coupling between zero-order states (ZOSs). Evidence is found for the role of torsional motion in facilitating the coupling between vibrations that particularly involves the lowest-wavenumber out-of-plane vibrational modes. The experiments are carried out on jet-cooled p-fluorotoluene, where the molecules are initially in the lowest two torsional levels. Here we concentrate on the 390-420 cm -1 features in the S1  S0 excitation spectrum, assigning the features seen in the 2D-LIF spectrum, aided by separate dispersed fluorescence spectra. The 2D-LIF spectra allow the overlapping contributions to be cleanly separated, including some that arise from vibrational-torsional coupling. Various coupling routes open up because of the different symmetries of the lowest two torsional modes; these combine with the vibrational symmetry to provide new symmetry-allowed vibration-torsion ('vibtor') interactions, and the role of the excited m = 1 torsional level is found to be significant.

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