The ultra-violet absorption spectra of fluorinated toluenes

Cave, W. T.; Thompson, H. W.

doi:10.1039/df9500900035

Cited by 32 publications

(6 citation statements)

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“…As mentioned before, combination bands at this energy are due to vibrations that are strongly coupled, e.g., through Fermi resonances. Finally, the UV spectrum of α,α,α,-trifluorotoluene was investigated in absorption and laser-induced fluorescence experiments. For the electronic transition S 0 → S 1 , the Franck−Condon active modes at energies below the (0,0) band (266 nm) were identified as ν 20 , ν 26 , ν 28 , ν 30 , ν 35 , and ν 38 (see listing of Table ).…”

Section: Near-ir and Uv Spectroscopy Assignments And Franck−condon Ac...mentioning

confidence: 99%

Vibrational Energy Relaxation of Selectively Excited Aromatic Molecules in Solution: The Effect of a Methyl Rotor and Its Chemical Substitution

et al. 2003

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Transient femtosecond IR-pump-UV-probe spectroscopy is employed to investigate the intramolecular vibrational energy redistribution (IVR) and the intermolecular vibrational energy transfer (VET) of benzene, toluene (CH 3 -C 6 H 5 ), and R,R,R,-trifluorotoluene (CF 3 -C 6 H 5 ) selectively excited in overtones or combination bands of C-H stretch vibrations in solution. Global IVR and VET rate coefficients are derived from the measured transient absorption profiles using a simple kinetic model. The study reveals the effect of a methyl rotor and the effect of methyl rotor fluorination on the mechanisms and time scales of IVR and VET in aromatic model systems. For the present case, it turned out that the methyl rotor in toluene is not simply an enhancer for IVR; however, its fluorination accelerates IVR significantly. These results suggest that the methyl rotor effect on an aromatic ring in solution is more subtle than expected from previous gas-phase studies. In particular, the corresponding relaxation rates in this case are not simply governed by the number of lowest order resonances, such as found for aliphatic molecules. Instead, in aromatic molecules also, the very large number of higher order anharmonic resonances may play a pronounced role. Because the IVR rates are not at all correlated with the total density of states, we conclude that intramolecular vibrational energy relaxation of a zeroth order C-H stretch overtone or combination vibration in these molecules is not in its statistical limit and that hierarchical IVR, such as known for isolated molecules, still survives to some extent in solution.Our results further suggest that VET rates are not always simply correlated with the lowest frequency modes of the molecules.

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Section: Near-ir and Uv Spectroscopy Assignments And Franck−condon Ac...mentioning

confidence: 99%

Vibrational Energy Relaxation of Selectively Excited Aromatic Molecules in Solution: The Effect of a Methyl Rotor and Its Chemical Substitution

et al. 2003

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“…[54,[83][84][85][86][87] For molecules with an aromatic chromophore, only a limited number of low-frequency ringdeformation modes are FC-active. [88][89][90][91] The pump and probe schemes for C À I-containing molecules and aromatic molecules are depicted schematically in Figures 1 a and b, respectively. Finally, during and after IVR, vibrational energy transfer to the solvent takes place and in turn decreases the absorption.…”

Section: Time-resolved Near-ir Overtone Pump and Uv Probementioning

confidence: 99%

Watching Photoinduced Chemistry and Molecular Energy Flow in Solution in Real Time

2003

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Energized molecules are the essential actors in chemical transformations in solution. As the rearrangement of bonds requires a movement of nuclei, vibrational energy is often the driving force for a reaction. Vibrational energy can be redistributed within the "hot" molecule, or relaxation can occur when molecules interact. Both processes govern the rates, pathways, and quantum yields of chemical transformations in solution. Unfortunately, energy transfer and the breaking, formation, and rearrangement of bonds take place on ultrafast timescales. This Review highlights experimental approaches for the direct, ultrafast measurement of photoinduced femtochemistry and energy flow in solution. In the first part of this Review, we summarize recent experiments on intra- and intermolecular energy transfer. The second part discusses photoinduced decomposition of large organic peroxides, which are used as initiators in free radical polymerization. The mechanisms and timescales of their decarboxylation determine the initial steps of polymerization and the microstructure of the polymer product.

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“…(Since we work under jet-cooled conditions, and since we only partially resolve rotational structure, we do not directly consider interactions involving rotations.) Earlier work on the S1  S0 transition in pFT has been reported by Cave and Thompson 22 , Cvitaš and Hollas 23 , Seliskar et al 24 and Okuyama et al 25 The latter two studies presented laser-induced fluorescence (LIF) spectra under jet-cooled conditions, giving assignments of some of the vibrational bands. Some of the low-wavenumber bands have been reassigned to vibration-torsion (vibtor) levels by Zhao, 3 and confirmed in recent work by our group 15 and that of Lawrance et al 16 In an earlier paper from our group, 14 we had used the assignments of Okuyama et al 25 in assigning ZEKE spectra recorded via various levels, unaware that some of the assignments of the lower-wavenumber features had been superseded by those in Zhao's thesis 3 -some of those latter reassignments are implicit in Ref.…”

Section: Introductionmentioning

confidence: 96%

Complexity surrounding an apparently simple Fermi resonance in p-fluorotoluene revealed using two-dimensional laser-induced fluorescence (2D-LIF) spectroscopy

Kemp

Whalley

Gardner

et al. 2019

The Journal of Chemical Physics

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Two-dimensional laser-induced fluorescence (2D-LIF) spectroscopy is a powerful tool allowing overlapped features in an electronic spectrum to be separated, and interactions between vibrations and torsions to be identified. Here the technique is employed to assign the 790-825 cm -1 region above the origin of the S1  S0 transition in para-fluorotoluene (pFT), which provides insight into the unusual time-resolved results of Davies and Reid [Phys. Rev. Lett. 109, 193004 (2012)]. The region is dominated by a pair of bands that arise from a Fermi resonance; however, the assignment is complicated by contributions from a number of overtones and combinations, including vibration-torsion ("vibtor") levels. The activity in the 2D-LIF spectra is compared to recently reported zero-electron-kinetic-energy (ZEKE) spectra [Tuttle et al. J. Chem. Phys. 146, 244310 (2017)] to arrive at a consistent picture of the energy levels in this region of the spectrum.

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The ultra-violet absorption spectra of fluorinated toluenes

Cited by 32 publications

References 0 publications

Vibrational Energy Relaxation of Selectively Excited Aromatic Molecules in Solution: The Effect of a Methyl Rotor and Its Chemical Substitution

Vibrational Energy Relaxation of Selectively Excited Aromatic Molecules in Solution: The Effect of a Methyl Rotor and Its Chemical Substitution

Watching Photoinduced Chemistry and Molecular Energy Flow in Solution in Real Time

Complexity surrounding an apparently simple Fermi resonance in p-fluorotoluene revealed using two-dimensional laser-induced fluorescence (2D-LIF) spectroscopy

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