METHYL ROTOR ACCELERATION OF VAN DER WAALS BOND DISSOCIATION. A SPECTROSCOPIC VIEW.
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Date
1991
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Ohio State University
Abstract
The molecules p-difluarobenzene (pDFB) and p-fluorotoluene (pFT) differ by the presence of a nearly free methyl rotor in the latter. It is well established by spectroscopy that the methyl rotor has a big effect on the intramolecular dynamics of these molecules, with two orders of magnitude methyl rotor acceleration of intramolecular vibrational energy redistribution (IVR). We have now begun to study the dissociation of the van der Waals complexes with argon. We find a similar acceleration of dissociation. The $S_{2}-S_{0}$ fluorescence spectra of pFT-Ar and pDFB-Ar complexes differ qualitatively. The dissociation rate is so accelerated in pFT-Ar that emission from the undissociated $S_{1}$ complex can no longer be observed. Without quantitative constraints, we can account for the increased dissociation rates by the proposition that the methyl rotor boosts the rate of IVR inside the complex itself.
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Author Institution: Department of Chemistry, Indiana University