The Influence of a Nearly Free Methyl Rotor on the Dynamics of Vibrational Predissociation and IVR
Intramolecular vibrational redistribution (IVR) rates can be profoundly changed by simple chemical modifications. An example occurs in the molecular pair p-difluorobenzene (pDFB) and p-fluorotoluene (pFT). These molecules are related by the replacement of a pDFB fluorine with a methyl group to produce pFT. IVR in 300 K gas phase molecules has been characterized for regions of the S1 manifold where the ring mode density is 100–2000 states per cm−1 [1,2]. The methyl substitution increases IVR rates by about a hundred-fold . The time scales change from 15–300 psec to sub-psec.
KeywordsInternal Rotation Ring Mode Fluorescence Excitation Spectrum Methyl Substitution Coupling Matrix Element
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