FLUORESCENCE SPECTRA OF p-DIFLUOROBENZENE IN A MOLECULAR BEAM, EVIDENCE FOR ROTATIONAL INVOLVEMENT IN INTRAMOLECULAR VIBRATIONAL REDISTRIBUTION
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Date
1983
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Ohio State University
Abstract
Examples of single vibronic level (SVL) fluorescence spectra displaying congestion exceeding that expected from thermal inhomogeneous broadening are abundant and have been used as evidence for intramolecular vibrational redistribution (IVR). Based on the congestion observed in SVL spectra, the onset of the IVR process has been shown to occur at low vibrational energies in the first excited singlet state where the vibrational density of states is on the order of unity. In order to account for the observed congestion, rotational involvement in IVR has been suggested as a means of coupling a larger number of vibronic levels. By comparing SVL spectra of p-difluorobenzene obtained at room temperature with those obtained in the cold conditions of a molecular beam, we have found evidence for rotational involvement in IVR. In the molecular beam the spectra observed show less congestion than the equivalent room temperature spectra, indicating that the onset of IVR occurs at higher vibrational energy in the low temperature case.
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Author Institution: Department of Chemistry Indiana, University Bloomington